82 research outputs found
On the computational complexity of portal and push-pull block puzzles
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 49-53).We classify the computational complexity of two types of motion planning problems represented in games. Portal, a popular video game, is shown to be NP-hard or PSPACE-complete depending on the game mechanics allowed. Push-pull block puzzles are games, similar to Sokoban, which involve moving a 'robot' on a square grid with obstacles and blocks that can be pushed or pulled by the robot into adjacent squares. We prove that push-pull block puzzles in 3D and push-pull block puzzles in 2D with thin walls are NP-hard to solve. We also show certain 3D push-pull block puzzles are PSPACE-complete. This work follows in a long line of algorithms and complexity work on similar problems Wil91, DDO00, Hof00, DHH04, DH01, DO92, DHH02, Cul98, DZ96, Rit10]. The 2D push-pull block puzzle also shows up in a number of video games, thus implying other results, further continuing the work on understanding video games as in Vig12, ADGV14, For10, Cor04.by Jayson Lynch.M. Eng
Hyperlocal Career Pathway Programs in New Hampshire: Collaborating to Support Youth at the Secondary/Postsecondary Transition
No full textCollege costs and persistent workforce shortages have prompted educators, policymakers, and employers to shift the conversation on the transition from high school from a narrow “college for all” emphasis to a broader “postsecondary education” and “career pathways” perspective. The timing of this shift coincides with current and anticipated workforce needs; by 2032, New Hampshire will have 197,000 positions available across its top 80 occupations, with labor force growth projected to fill only 6,100 of those jobs.
Some commentators argue that broadening options to include career and technical education, certificates, and 2-year degrees is essential for realizing equity gains. Successfully building such pathways cannot be accomplished by educational institutions alone; it requires collaboration across public, nonprofit, and private sectors, as well as financial and policy incentives that reduce barriers and risks.
In this paper, author Jayson Seaman describes an innovative effort to address these challenges in New Hampshire, focusing on programs following a “hyperlocal” approach to career pathway development that simultaneously address specific, local industry, community, and individual needs. Their purpose is to increase the likelihood of social mobility by using career exposure and hands-on involvement to spur interest and motivation toward additional education and training in promising fields. The research reported here focused on programs that target youth approaching the secondary-postsecondary transition.
The study’s main findings show what it takes for career pathway sites to realize effective collaboration among partners and provide learners with a positive experience. The paper concludes with a discussion about areas of ongoing need both within and outside of individual pathway programs
Monte Carlo simulations of a physical cryptographic warhead verification protocol using nuclear resonance fluorescence
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Page 99 blank. Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 93-98).Future multilateral nuclear arms reduction efforts will require technologies for the verification of treaty compliance. In particular, warheads slated for dismantlement will need to be verified for authenticity without revealing any sensitive weapons design information to international inspectors. Recent efforts have investigated physical cryptographic verification protocols that attempt to solve this treaty verification problem by using physics processes rather than electronics to encrypt sensitive information. The physical cryptographic protocol simulated in this thesis exploits the isotope-specific nature of nuclear resonance fluorescence (NRF) measurements to provide a strong indicator of the authenticity of a warhead. To protect against sensitive information leakage, the NRF signal from the warhead is convoluted with that of an encrypting foil containing the same isotopes as the warhead but in unknown amounts. The convoluted spectrum from a candidate warhead is then statistically compared against that from an authenticated template warhead to determine whether the candidate itself is authentic. This work presents the initial Geant4 Monte Carlo simulations of the physical cryptographic warhead verification protocol. Using a 2.7 MeV endpoint bremsstrahlung beam, a template warhead is interrogated. Several hoax geometries are also compared against the template to show the protocol's robustness against cheating. Isotopic hoaxes in which weapons-grade plutonium is replaced with reactor-grade plutonium or depleted uranium are shown to be detectable in realistic measurement times. An optimized geometric hoax that mimics the areal densities and attenuations of the authentic template warhead along one axis can also be detected with a second measurement under a different projection. Results of the simulations as well as future research objectives will be presented and discussed.by Jayson Robert Vavrek.S.M
A semi-autonomous robotic system with alignment control for the occluded object using visual servoing and computational intelligence
No full textAligning a mobile X-ray system in challenging environments, such as bomb-surrounded areas, poses difficulties due to safety concerns and occlusion. This study introduces a novel approach employing 6D object pose estimation and pose correction by integrating DeepLabV3 and iterative dense fusion into the visual servoing mechanism. The robotic system exhibits enhanced accuracy in detecting and aligning the occluded known 3D object model x-ray source to film. Evaluation metrics, including intersection-over-union and mean average, demonstrate high accuracy percentages for detecting the body (98.91%), handle (96.57%), and aperture (89.54%). The mean IoU for each part of the 3D model portable X-ray source ranges from 65.69% to 76.42%. Pose estimation accuracy, assessed through the ADD metric, indicates superior performance for static pose estimation closer to the camera. Dynamic pose estimation exhibits higher average ADD metrics in scenes with total occlusion. The robustness metric reveals lower lost tracking counts in scenes without occlusion, emphasizing the algorithm\u27s challenges in fully occluded scenarios. The film handler alignment system, characterized by kinematic formulation and actuator calibration data, shows minimal errors in X and Y actuation
Development of an isotope-sensitive warhead verification technique using nuclear resonance fluorescence
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 93-99).Nearly three decades after the end of the Cold War, nuclear arms control remains a pressing global issue. Despite obligations under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) to make 'good-faith efforts' to disarm their nuclear arsenals, the United States and Russia still maintain thousands of nuclear warheads. Progress towards complete disarmament has been gradual due to a variety of socio-political barriers, but future efforts towards nuclear arms reduction will face an additional technological hurdle: no technology exists to verify that warheads slated for dismantlement are authentic without revealing any sensitive weapons design information in the process. Despite several decades of research, no technology has solved this apparent paradox between information security and confidence in a warhead verification measurement.Recent work by Kemp, Danagoulian, Macdonald, and Vavrek [1] has produced a novel physical cryptographic verification protocol that approaches this treaty verification problem by exploiting the isotope-specific nature of nuclear resonance fluorescence (NRF) measurements to verify the authenticity of a warhead. To protect sensitive information, the NRF signal from the warhead is convolved with that of an encryption foil that contains key warhead isotopes in amounts unknown to the inspector. The convolved spectrum from a candidate warhead is then statistically compared against that from an authenticated template warhead to determine whether the candidate itself is authentic. Since only the final, convolved spectra are observable, and the detailed foil construction is unknown to the inspector, sensitive information about the warhead is encrypted by physics rather than by software or electronics.In this thesis, we performed proof-of-concept NRF warhead verification experiments at the High Voltage Research Laboratory (HVRL) at MIT [2]. Using high-purity germanium (HPGe) detectors, we measured NRF spectra produced by the interrogation of proxy 'genuine' and 'hoax' objects by a 2.52 MeV endpoint bremsstrahlung beam. The observed differences in NRF intensities near 2.2 MeV indicate that the physical cryptographic protocol can distinguish between proxy genuine and hoax objects with high confidence. Extrapolations to thicker warheads and dedicated verification facilities indicate that realistic warhead verification measurements could be made on the order of hours. In support of these and future NRF experiments, we also improved and benchmarked the G4NRF code for the simulation of NRF in Geant4 [3]. We first constructed a high-accuracy semi-analytical model for the expected NRF count rate in both simple homogeneous and more complex heterogeneous geometries.We then performed Geant4+G4NRF simulations with these geometries, and found agreement in NRF rates predicted by the semi-analytical model and observed in the simulation at a level of ~1% in simple test cases and ~3% in the more realistic complex scenarios. These results improve upon the ~20% level of the initial G4NRF benchmarking study and establish a highly-accurate NRF framework for Geant [4]. Finally, we conducted a G4NRF validation study using the NRF data taken during the warhead verification experiments [4]. Agreement between the absolute NRF count rates observed in the data and predicted by extensive Geant4+G4NRF modeling validate the combined Geant4+G4NRF model to within ~20% in the 238U NRF transitions and 9% in 27Al, for an average 14% discrepancy across the entire study. Additionally, agreement between the model and data in relative NRF rates is found at the level of .5%.Such agreement in both relative and absolute analyses provides good predictive capability for the design and analysis of future NRF experiments using G4NRF, whether for warhead verification or other applications.by Jayson Robert Vavrek.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Nuclear Science and Engineerin
A PC-based controller for the computer numerically-controlled (CNC) laser machine
No full textThis study presents the development of a PC-based controller for the 3-axis computer numerically-controlled (CNC) LASER machine. This includes the use of an MK-II motion controller board in controlling the three (3) Ezi-Servo stepper motors and in enabling the LASER output from the Synrad firestar f201. The LASER power output is controlled using a developed PWM controller. The machine was tested both in functional and performance testing. In terms of performance, it can cut mild steel and stainless steel with thickness of 2 mm and 1 mm, respectively. PLT extension file was used for the g-code toolpath of the CNC LASER machine system
A pulse-width modulation (PWM) LASER power controller for the 3-axis computer numerically-controlled (CNC) LASER machine: Support program for the productivity and competitiveness of the metals and engineering industries
No full textA pulse-width modulation (PWM) laser poer controller for the 3-Axis Computer Numerically-Controlled (CNC) laser machine: support program for the productivity and competitiveness of the metals and engineering sciences
No full textDevelopment of an automatic tool changer (ATC) system for the 3-axis computer numerically-controlled (CNC) router machine: Support program for the productivity and competitiveness of the metals and engineering industries
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