A cold ejector for closed-cycle helium refrigerators

The test results are presented of an initial cold helium ejector design that can be installed on a closed cycle refrigerator to provide refrigeration at temperatures below 4.2 K. The ejector, test apparatus, instrumentation, and test results are described. Tests were conducted both at room temperature and at cryogenic temperatures to provide operational experience with the ejector as well as for future use in the subsequent design of an ejector that will provide refrigeration at temperatures below 3 K

For Whom the School Bell Tolls but Not the Statute of Limitations: Minors and the Individuals with Disabilities Education Act

This Article explores whether claims under the federal special education statute should be tolled on account of minority. Adult disabled students typically assert this type of tolling claim when alleging statutory violations dating back ten or more years, when they were minors. However this tolling claim is decided, there may be undesired results. First, even if the student has a very strong case, the merits are never reached if the court dismisses the hearing request as untimely. Second, if the hearing request is timely and the case proceeds to the merits, the student must remain in her current educational placement, potentially at great cost, during the lengthy IDEA hearing and appeals process as mandated by the IDEA\u27s stay put provision. Moreover, the school may face difficulties defending the claim on the merits because under the IDEA, schools must allow parents and adult students to request destruction of their special education records to the extent the records are not currently required in order to provide services. Finally, unique challenges arise for schools because parents help develop their child\u27s special education program. Accordingly, schools rely on both the parents\u27 approval of the educational program, as well as the parents\u27 choice not to request a due process hearing for their minor child. The IDEA specifically assigns the right to make this decision to the parents of minor students, and not the minor students themselves, as part of the IDEA\u27s panoply of procedural safeguards. Congress first addressed statute of limitations issues under the IDEA in the 2004 amendments. This Article surveys the relevant case law on whether to borrow tolling provisions from state statutes and reveals great variation among the courts. Specifically, the courts vary in their adherence to Supreme Court precedent, their application of this precedent, and their conclusions about whether tolling on account of minority should apply in IDEA disputes. The Article concludes that, because of the unique role the IDEA assigns to parents, the correct approach under the pre-2004 amendments is not to toll claims for minors. The Article then examines the new IDEA language, which creates explicit statutes of limitation, but does not explicitly address the issue of tolling for minor students. Consequently, in future litigation, students and parents are likely to claim that tolling for minors should be judicially read into the IDEA\u27s new statutes of limitations. However, this Article concludes, through an application of the Supreme Court\u27s guidance in this area, that a tolling rule for legal minors should not be read into the IDEA\u27s new statutes of limitation. Tolling for minors is inconsistent with congressional intent as evidenced by the pre-2004 amendments analysis, and further strengthened by the new amendments. Finally, the consequences of tolling are harsher than those of not tolling

Water Injection Feasibility for Boeing 747 Aircraft

Can water injection be offered at a reasonable cost to large airplane operators to reduce takeoff NO( sub x) emissions? This study suggests it may be possible. This report is a contract deliverable to NASA Glenn Research Center from the prime contractor, The Boeing Commercial Airplane Company of Seattle, WA. This study was supported by a separate contract to the Pratt & Whitney Engine Company of Hartford, CT (contract number NNC04QB58P). Aviation continues to grow and with it, environmental pressures are increasing for airports that service commercial airplanes. The feasibility and performance of an emissions-reducing technology, water injection, was studied for a large commercial airplane (e.g., Boeing 747 with PW4062 engine). The primary use of the water-injection system would be to lower NOx emissions while an important secondary benefit might be to improve engine turbine life. A tradeoff exists between engine fuel efficiency and NOx emissions. As engines improve fuel efficiency, by increasing the overall pressure ratio of the engine s compressor, the resulting increased gas temperature usually results in higher NOx emissions. Low-NO(sub x) combustors have been developed for new airplanes to control the increases in NO(sub x) emissions associated with higher efficiency, higher pressure ratio engines. However, achieving a significant reduction of NO(sub x) emissions at airports has been challenging. Using water injection during takeoff has the potential to cut engine NO(sub x) emissions some 80 percent. This may eliminate operating limitations for airplanes flying into airports with emission constraints. This study suggests an important finding of being able to offer large commercial airplane owners an emission-reduction technology that may also save on operating costs

Future Fuel Scenarios and Their Potential Impact to Aviation

In recent years fuel prices have been growing at a rapid pace. Current conservative projections predict that this is only a function of the natural volatility of oil prices, similar to the oil price spikes experienced in the 1970s. However, there is growing concern among analysts that the current price increases may not only be permanent, but that prices may continue to increase into the future before settling down at a much higher level than today. At high enough fuel prices, the aircraft industry would become very sensitive to fuel price. In this paper, the likelihood of fuel price increase is considered in three different price increase scenarios: "low," "medium," and "high." The impact of these scenarios on the aviation industry and alternatives are also addressed

Alternate Fuels for Use in Commercial Aircraft

The engine and aircraft Research and Development (R&D) communities have been investigating alternative fueling in near-term, midterm, and far-term aircraft. A drop in jet fuel replacement, consisting of a kerosene (Jet-A) and synthetic fuel blend, will be possible for use in existing and near-term aircraft. Future midterm aircraft may use a biojet and synthetic fuel blend in ultra-efficient airplane designs. Future far-term engines and aircraft in 50-plus years may be specifically designed to use a low- or zero-carbon fuel. Synthetic jet fuels from coal, natural gas, or other hydrocarbon feedstocks are very similar in performance to conventional jet fuel, yet the additional CO2 produced during the manufacturing needs to be permanently sequestered. Biojet fuels need to be developed specifically for jet aircraft without displacing food production. Envisioned as midterm aircraft fuel, if the performance and cost liabilities can be overcome, biofuel blends with synthetic jet or Jet-A fuels have near-term potential in terms of global climatic concerns. Long-term solutions address dramatic emissions reductions through use of alternate aircraft fuels such as liquid hydrogen or liquid methane. Either of these new aircraft fuels will require an enormous change in infrastructure and thus engine and airplane design. Life-cycle environmental questions need to be addressed

Preliminary Comparison of Two Negative Reinforcement Schedules to Reduce Self-Injury

This study compared the effectiveness of differential negative reinforcement of other behavior (DNRO) and alternative behavior (DNRA) for reducing self-injurious tantrums maintained by escape from demands in a 4-year-old girl with severe retardation. Both DNRA and DNRO reduced self-injury and increased independent performance of two tasks (tooth brushing and bathing); however, improvement on both measures was greater with the DNRA intervention

In-office needle arthroscopic assessment after primary ACL repair. Short-term results in 15 patients

Purpose: In-office needle arthroscopy has been reported as a diagnostic tool for different knee pathologies. In addi- tion, ACL repair has seen a resurgence with the advent of innovative orthopedic devices. The aim of this study was to assess clinical, radiological, and in-office needle arthroscopic findings in 15 adult patients who underwent acute (within 14 days from injury) anterior cruciate ligament (ACL) repair. Methods: Fifteen patients voluntarily participated in the study. A second-look arthroscopy was performed with an in-office needle arthroscopy at an average of 7.2 months after the primary repair. The parameters included in the investigation were the continuity of the anatomical footprint of the repaired ACL, subjective assessment of the ACL tension with the probe, and synovial coverage of the ACL. All patients had a Magnetic Resonance Imaging (MRI) at 6 months after repair and an arthrometric evaluation with the KT-1000. Clinical evaluation with the scores, Tegner Lysholm Knee Scoring Scale (TLKSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) was performed at the final follow-up of 2 years. Moreover, a correlation between the characteristics of ACL appearance at the time of the second look in-office needle arthroscopy, MRI and KT-1000 was performed. Results: The mean TLKSS was 97.86, the mean KOOS was 98.08 and the mean subjective IKDC was 96.71. The objec- tive IKDC was A in 10 patients and B in 5 patients. ACL healing was graded as A in 11 patients and B in 4 patients. Synovial coverage was graded as good in 10 patients and fair in 5 while MRI assessment showed a type I ACL in 10 patients, type II in 4 patients and type III in 1 patient. Conclusion: In-office needle arthroscopy is a reliable tool to assess the condition of a repaired ACL. In addition, ACL repair performed in acute proximal tears demonstrated excellent clinical results

Design of Force Fields from Data at Finite Temperature

We investigate the problem of how to obtain the force field between atoms of an experimentally determined structure. We show how this problem can be efficiently solved, even at finite temperature, where the position of the atoms differs substantially from the ground state. We apply our method to systems modeling proteins and demonstrate that the correct potentials can be recovered even in the presence of thermal noise.Comment: 10 pages, 1 postcript figure, Late

Can Water-Injected Turbomachines Provide Cost-Effective Emissions and Maintenance Reductions?

An investigation has been performed to evaluate the effect of water injection on the performance of the Air Force Research Laboratory (AFRL, Wright-Patterson Air Force Base (WPAFB)) experimental trapped vortex combustor (TVC) over a range of fuel-to-air and water-to-fuel ratios. Performance is characterized by combustor exit quantities: temperature and emissions measurements using rakes, and overall pressure drop, from upstream plenum to combustor exit. Combustor visualization is performed using gray-scale and color still photographs and high-frame-rate videos. A parallel investigation evaluated the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid fueled combustor (e.g., TVC) that uses water injection for control of pollutant emissions and turbine inlet temperature. Generally, reasonable agreement is found between data and NO(x) computations. Based on a study assessing the feasibility and performance impact of using water injection on a Boeing 747-400 aircraft to reduce NO(x) emissions during takeoff, retrofitting does not appear to be cost effective; however, an operator of a newly designed engine and airframe might be able to save up to 1.0 percent in operating costs. Other challenges of water injection will be discussed