Test stand system for vacuum chambers

A test stand system for supporting test items in a vacuum chamber is described. The system consists of a frame adapted to conform to the inside of the vacuum chamber and supporting a central vertical shaft. The shaft rotates on bearings located at each end of the shaft. Several vertically spaced plates which fixed to the vertical shaft may be adjusted for height to support the test equipment as required. The test equipment may be rotated during tests without disturbing the vacuum by a manually actuated drive external to the vacuum chamber

Global optimality of extremals: An example

The question of the existence and location of Darboux points is crucial for minimally sufficient conditions for global optimality and for computation of optimal trajectories. A numerical investigation is presented of the Darboux points and their relationship with conjugate points for a problem of minimum fuel, constant velocity, and horizontal aircraft turns to capture a line. This simple second order optimal control problem shows that ignoring the possible existence of Darboux points may play havoc with the computation of optimal trajectories

Proper conformal symmetries in SD Einstein spaces

Proper conformal symmetries in self-dual (SD) Einstein spaces are considered. It is shown, that such symmetries are admitted only by the Einstein spaces of the type [N]x[N]. Spaces of the type [N]x[-] are considered in details. Existence of the proper conformal Killing vector implies existence of the isometric, covariantly constant and null Killing vector. It is shown, that there are two classes of [N]x[-]-metrics admitting proper conformal symmetry. They can be distinguished by analysis of the associated anti-self-dual (ASD) null strings. Both classes are analyzed in details. The problem is reduced to single linear PDE. Some general and special solutions of this PDE are presented

Competitive Prices and Organizational Choices

We construct a price-theoretic model of integration decisions and show that these choices may adversely affect consumers, even in the absence of monopoly power in supply and product markets. Integration is costly to implement but is effective at coordinating production decisions. The price of output helps to determine the organizational form chosen: there is an inverted-U relation between the degree of integration and product prices. Moreover, organizational choices affect output: integration is more productive than non-integration at low prices, and less productive at high prices. Since shocks to industries affect product prices, reorganizations are likely to take place in coordinated fashion and be industry specific, consistent with the evidence. Since the price range in which integration maximizes productivity generally differs from the one in which it maximizes managerial welfare, organizational choices will often be second-best inefficient. We show that there are instances in which entry of low-cost suppliers can hurt consumers by changing the terms of trade in the supplier market, thereby inducing reorganizations that raise prices.

Managerial Firms, Vertical Integration, and Consumer Welfare

We show that vertical integration decisions of managers may affect adversely consumers even in the absence of monopoly power in either supply or product markets. This effect is most likely to come about when demand is initially high and there is a negative supply shock or when demand is low and there is a positive demand shock. The results are robust to the introduction of active shareholders and to other extensions.

Competing for Ownership

We develop a tractable model of the allocation of ownership and control in firms in competitive markets that permits study of how the scarcity of assets in the market translates into control allocations inside the organization. The model identifies a price-like mechanism whereby local liquidity or productivity shocks propagate and lead to widespread organizational restructuring. Firms will be more integrated when the terms of trade are more favorable to the short side of the market, when liquidity is unequally distributed among existing firms and following a uniform increase in productivity. Shocks to the first two moments of the liquidity distribution have multiplier effects on the corresponding moments of the distribution of ownership.

Extension of the tridiagonal reduction (FEER) method for complex eigenvalue problems in NASTRAN

As in the case of real eigenvalue analysis, the eigensolutions closest to a selected point in the eigenspectrum were extracted from a reduced, symmetric, tridiagonal eigenmatrix whose order was much lower than that of the full size problem. The reduction process was effected automatically, and thus avoided the arbitrary lumping of masses and other physical quantities at selected grid points. The statement of the algebraic eigenvalue problem admitted mass, damping, and stiffness matrices which were unrestricted in character, i.e., they might be real, symmetric or nonsymmetric, singular or nonsingular

Eigenvalue extraction in NASTRAN by the tridiagonal reduction (FEER) method: Real eigenvalue analysis

The development of the tridiagonal reduction method and its implementation in NASTRAN are described for real eigenvalue analysis as typified by structural vibration and buckling problems. This method is an automatic matrix reduction scheme whereby the eigensolutions in the neighborhood of a specified point in the eigenspectrum can be accurately extracted from a tridiagonal eigenvalue problem whose order is much lower than that of the full problem. The process is effected without orbitrary lumping of masses or other physical quantities at selected node points and thus avoids one of the basic weaknesses of other techniques

Ethical approaches to family planning in Africa

Africa has historically provided the geographical flashpoint of ethical issues relating to family planning programs. Until recently in Sub-Saharan Africa, advocacy of family planning by non-Africans was unacceptable and by Africans politically inadvisable. This has changed in the 1980s. The health rationale for family planning is backed by strong evidence, especially in Africa, where infant and maternal mortality and morbidity rates are high. Population growth in many African countries impedes development, which cannot keep up with needs. Earlier attempts to offer family planning aid were often politically inept and endangered the needed partnership between donor and developing countries. Theoretical arguments and abstract demographic projections are less persuasive than carefully designed programs geared to the health and well-being of communitities that help plan them. Increased cooperation between donor and developing countries has helped resolve some of the ethical difficulties that beset family planning programs. This report summarizes many of the practical, ethical and cultural considerations in making family planning aid acceptable.Health Monitoring&Evaluation,Adolescent Health,Agricultural Knowledge&Information Systems,Gender and Health,Early Child and Children's Health