5,102 research outputs found
Bijections behind the Ramanujan Polynomials
The Ramanujan polynomials were introduced by Ramanujan in his study of power
series inversions. In an approach to the Cayley formula on the number of trees,
Shor discovers a refined recurrence relation in terms of the number of improper
edges, without realizing the connection to the Ramanujan polynomials. On the
other hand, Dumont and Ramamonjisoa independently take the grammatical approach
to a sequence associated with the Ramanujan polynomials and have reached the
same conclusion as Shor's. It was a coincidence for Zeng to realize that the
Shor polynomials turn out to be the Ramanujan polynomials through an explicit
substitution of parameters. Shor also discovers a recursion of Ramanujan
polynomials which is equivalent to the Berndt-Evans-Wilson recursion under the
substitution of Zeng, and asks for a combinatorial interpretation. The
objective of this paper is to present a bijection for the Shor recursion, or
and Berndt-Evans-Wilson recursion, answering the question of Shor. Such a
bijection also leads to a combinatorial interpretation of the recurrence
relation originally given by Ramanujan.Comment: 18 pages, 7 figure
Radiation Hardness of High-Q Silicon Nitride Microresonators for Space Compatible Integrated Optics
Integrated optics has distinct advantages for applications in space because
it integrates many elements onto a monolithic, robust chip. As the development
of different building blocks for integrated optics advances, it is of interest
to answer the important question of their resistance with respect to ionizing
radiation. Here we investigate effects of proton radiation on high-Q silicon
nitride microresonators formed by a waveguide ring. We show that the
irradiation with high-energy protons has no lasting effect on the linear
optical losses of the microresonators
Helicopter mathematical models and control law development for handling qualities research
Progress made in joint NASA/Army research concerning rotorcraft flight-dynamics modeling, design methodologies for rotorcraft flight-control laws, and rotorcraft parameter identification is reviewed. Research into these interactive disciplines is needed to develop the analytical tools necessary to conduct flying qualities investigations using both the ground-based and in-flight simulators, and to permit an efficient means of performing flight test evaluation of rotorcraft flying qualities for specification compliance. The need for the research is particularly acute for rotorcraft because of their mathematical complexity, high order dynamic characteristics, and demanding mission requirements. The research in rotorcraft flight-dynamics modeling is pursued along two general directions: generic nonlinear models and nonlinear models for specific rotorcraft. In addition, linear models are generated that extend their utilization from 1-g flight to high-g maneuvers and expand their frequency range of validity for the design analysis of high-gain flight control systems. A variety of methods ranging from classical frequency-domain approaches to modern time-domain control methodology that are used in the design of rotorcraft flight control laws is reviewed. Also reviewed is a study conducted to investigate the design details associated with high-gain, digital flight control systems for combat rotorcraft. Parameter identification techniques developed for rotorcraft applications are reviewed
Rotorcraft handling-qualities design criteria development
Joint NASA/Army efforts at the Ames Research Center to develop rotorcraft handling-qualities design criteria began in earnest in 1975. Notable results were the UH-1H VSTOLAND variable stability helicopter, the VFA-2 camera-and-terrain-board simulator visual system, and the generic helicopter real-time mathematical model, ARMCOP. An initial series of handling-qualities studies was conducted to assess the effects of rotor design parameters, interaxis coupling, and various levels of stability and control augmentation. The ability to conduct in-flight handling-qualities research was enhanced by the development of the NASA/Army CH-47 variable-stability helicopter. Research programs conducted using this vehicle include vertical-response investigations, hover augmentation systems, and the effects of control-force characteristics. The handling-qualities data base was judged to be sufficient to allow an update of the military helicopter handling-qualities specification, MIL-H-8501. These efforts, including not only the in-house experimental work but also contracted research and collaborative programs performed under the auspices of various international agreements. The report concludes by reviewing the topics that are currently most in need of work, and the plans for addressing these topics
Conflict Resolution Satisfaction and IS Program Effectiveness: Constructive Controversy Theory
Conflict occurrence during information systems (IS) development/implementation is an unavoidable phenomenon. Conflict strains interactions and trust, leads to further conflict, and has a negative effect on system implementation success. Therefore, resolving conflict that arises during the IS implementation process has been a crucial issue for decades. Unfortunately, the existing empirical evidences were not consistent with this conventional wisdom and lacking of a theoretical explanation. We argue that the integrative conflict management is an effective mechanism for conflict resolution under the multi-project system development context. We construct a model using controversy conflict theory in order to explain the effect of conflict resolution on IT projects implementation effectiveness. We test the model using data from 183 large-scale IT implementation projects. Our model and findings support our theory that integrative conflict management supports effective conflict resolution and program outcomes
Activity of anidulafungin in a murine model of Candida krusei infection: evaluation of mortality and disease burden by quantitative tissue cultures and measurement of serum (1,3)-beta-D-glucan levels.
Experience with anidulafungin against Candida krusei is limited. Immunosuppressed mice were injected with 1.3 x 10(7) to 1.5 x 10(7) CFU of C. krusei. Animals were treated with saline, 40 mg/kg fluconazole, 1 mg/kg amphotericin B, or 10 and 20 mg/kg anidulafungin for 5 days. Anidulafungin improved survival and significantly reduced the number of CFU/g in kidneys and serum beta-glucan levels
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