Nonlinear and distributed parameter models of the mini-mast truss

Large spacecraft such as Space Station Freedom employ large trusses in their construction. The structural dynamics of such trusses often exhibit nonlinear behavior and little damping which can impact significantly the performance of control systems. The Mini-MAST truss was constructed to research such structural dynamics and control systems. The Mini-MAST truss is an object of study for the guest investigator program as part of NASA's controls-structures interaction program. The Mini-MAST truss is deployable and about 65 ft long. Although the bending characteristics of the Mini-MAST truss are essentially linear, the angular deflection under torsional loading has exhibited significant hysteresis and nonlinear stiffness. It is the purpose to develop nonlinear and distributed parameter models of the truss and to compare the model dynamics with actual measurements. Distributed parameter models have the advantage of requiring fewer model parameters. A tangent function is used to describe the nonlinear stiffness in torsion, partly because of the convenience of its easily expressed inverse. Hysteretic slip elements are introduced and extended to a continuum to account for the observed hysteresis in torsion. The contribution of slipping to the structural damping is analyzed and found to be strongly dependent on the applied loads. Because of the many factors which affect the damping and stiffness in a truss, it is risky to assume linearity

Nondestructive leak testing

Method provides opportunity to effect repairs without compromising integrity of enclosed circuitry or mechanism by loss of atmosphere or by ingestion of foreign matter or gas. It is possible to detect leaks in modules which are sealed while fully evacuated, partially evacuated, or containing some form of gas

Handling Cases of Willful Exposure Through HIV Partner Counseling and Referral Services

Cases of willful exposure reveal the existing and future risks to the public health (especially women) which may be presented by individuals who willfully expose others to HIV through unsafe sexual or needle-sharing behaviors. In response to a documented case of willful exposure, a PCRS counselor or other public health official may, in his or her professional judgment, decide to act to avert a legitimate public health threat to known or unknown persons in the community. Yet handling such cases raises difficult issues in law, ethics, and public health practice. Public health authorities may be unable or ill-equipped to successfully control risks of this type for several reasons: (1) they may lack sufficient resources to properly investigate these cases; (2) they may lack knowledge or jurisdiction over the individual who willfully exposes others to HIV once his behaviors extend into other communities; and (3) they are bound to maintain the confidentiality of sensitive information they obtain from PCRS. How do health care workers and public health departments balance the duty to maintain the privacy of public health information related to PCRS against their obligation to fulfill a partner\u27s right to know of their exposure to infection? What are the legal powers and duties of public health departments to protect the health and safety of individuals as part of their mission to protect the public health? What is the role of the criminal law concerning persons who may intentionally or knowingly attempt to infect others with HIV or other communicable diseases

Personal Privacy and Common Goods: A Framework for Balancing Under the National Health Information Privacy Rule

In this Article, we discuss how these principles for balancing apply in a number of important contexts where individually identifiable health data are shared. In Part I, we analyze the modern view favoring autonomy and privacy. In the last several decades, individual autonomy has been used as a justification for preventing sharing of information irrespective of the good to be achieved. Although respect for privacy can sometimes be important for achieving public purposes (e.g., fostering the physician/patient relationship), it can also impair the achievement of goals that are necessary for any healthy and prosperous society. A framework for balancing that strictly favors privacy can lead to reduced efficiencies in clinical care, research, and public health. We reason that society would be better served, and individuals would be only marginally less protected, if privacy rules permitted exchange of data for important public benefits. In Part II, we explain the national health information privacy regulations: (1) what do they cover?; (2) to whom do they apply?; and (3) how do they safeguard personal privacy? Parts III and IV focus on whether the standards adhere, or fail to adhere, to the privacy principles discussed in Part I. In Part III, we examine two autonomy rules established in the national privacy regulations: informed consent (for uses or disclosures of identifiable health data for health-care related purposes) and written authorization (for uses or disclosures of health data for non-health care related purposes). We observe that the informed consent rule is neither informed nor consensual. The rule is likely to thwart the effective management of health organizations without benefiting the individual. Requiring written authorization, on the other hand, protects individual privacy to prevent disclosures to entities that do not perform health-related functions, such as employers and life insurers. In Part IV, we examine various contexts in which data can be shared for public purposes under the national privacy rule: public health, research, law enforcement, familial notification, and commercial marketing. We apply our framework for balancing in each context and observe the relative strengths and weaknesses of the privacy regulations in achieving a fair balance of private and public interests

Zika Virus and Global Health Security

Americans are largely apathetic about the risks of Zika virus and Congress cannot agree on preparedness funding. Strategies to counter the spread of Zika by the World Health Organisation (WHO) grossly underestimate the disease’s impact. WHO and member countries lack sufficient resources to respond. Consequences of fiscal apathy can be measured in lives lost and long-term disabilities. Zika prevention is a matter of global health security. The epidemiologic brunt of Zika in South America falls largely on vulnerable women at heightened risk of exposure through mosquitoes and sexual transmission. Resulting transmission to fetuses and infants will have generational impacts in South American and Caribbean countries, as well as the U.S. Global costs to address Zika infections among infected infants will exceed hundreds of billions (U.S. dollars). WHO and some U.S. leaders, including President Obama, correctly assert that Zika threatens national and global security similar to humanitarian crises, climate change, and war. Words alone, however, are not enough. Global recognition of this public health crisis must stimulate greater investment in preventing negative repercussions

Is the United States Prepared for a Major Zika Virus Outbreak?

Zika virus has emerged as a global public health crisis with active transmission in the Americas and Caribbean. The World Health Organization (WHO) declared a Public Health Emergency of International Concern (PHEIC), and recently WHO reported there is a scientific consensus that Zika is a cause of microcephaly and Guillain-Barré syndrome (GBS). In the U.S. the Centers for Disease Control and Prevention (CDC) activated its emergency operations center at its highest capacity. President Obama requested $1.86 billion in emergency funding. Shamefully, Congress has yet to appropriate the funding needed for Zika preparedness, and the President has had to reallocate Ebola funding for Zika prevention. Although none of the continental states has reported local mosquito-borne transmission, federal authorities are amplifying the potential for Zika to affect national security. The virus already severely threatens Puerto Rico. Travelers visiting or returning to the United States could likely escalate the spread of Zika via sexual transmission. The virus may spread across a majority of US states including large cities where Aedes species mosquitos are active. Is the U.S. prepared for Zika? America\u27s highly functioning health system will help, but signs of unpreparedness remain due to insufficient resources and variable legal authorities

Finance and its reform : beyond laissez-faire

That the financial sector should be liberalized was the orthodox view in the mid-1970s, during a pendulum swing toward reliance on the free market. In the early 1980s, the pendulum swung back to the left, based partly on evidence - especially from Latin America - that overly rapid reform had real costs, and partly on an increased appreciation of financial market failure. Blind adherence to free market principles was no longer appropriate. Now a counter-counterrevolution is in sight, with some swing back toward the view that the market makes a mess of it, but the government makes it even worse. The authors agree that market-oriented financial systems appear to do a better job than systems with extensive government involvement, but contend that the assumption that perfect competition will solve all problems in finance - especially in banking - can be dangerous. Information problems, implicit or explicit government guarantees associated with the payments system make banks unique. Governments implicitly recognize banking's uniqueness - few allow just anyone to enter banking - but public pronouncements and observers'recommendations often favor a move to more competition. Perfect competition, however, is optimal under the assumption, among others, of no government guarantee. In fact, most governments differ only in how explicit they are about their deposit insurance schemes. The financial reforms most likely to succeed are those that give banks an incentive to engage in safe and sound banking. When excessive competition is allowed, the charter value of banking diminishes to the point that it is no longer profitable for bankers to behave prudently. A consideration of finance's role, and a look at how reforming economies have fared, suggest also that gradual reform is often to be preferred in this domain. Deregulation of credit markets and interest rates can be counterproductive in unstable macroeconomic conditions and when banks are unsophisticated or have weak balance sheets. And changes in the charter value may evolve only slowly after reform. Faster progress and greater efforts should be made, however, in bank supervision and regulation and in institutional development, including accounting, auditing, legal and judicial reform, and training (of bankers and other finance professionals). In sum, many economies would benefit from less government intervention in financial markets, but the prescription should not be abrupt or total government withdrawal from the financial sector. Rather than intervening heavily in credit allocation decisions, governments should focus on doing what only they can do: providing an enabling environment for the private financial and nonfinancial sectors, and ensuring that financial operations are safe and sound.Environmental Economics&Policies,Banks&Banking Reform,Financial Intermediation,Economic Theory&Research,Financial Crisis Management&Restructuring

Control-structures Interaction Test of the LACE Satellite

It is clear that additional experience and validation of Control Structures Interaction (CSI) techniques are needed in controlling the structural dynamics of flexible spacecraft. It is also clear that the effects of the space environment such as weightlessness dictate that this be done in space. Unfortunately, orbital tests are difficult to achieve because of the high cost of the test article, the launch into orbit, the instrumentation, and communication systems. The Low-power Atmospheric Compensation Experiment (LACE) Satellite has provided an opportunity to achieve a CSI test in space for very little cost. First, the CSI test rode piggy-back and did not interfere with the primary objective of LACE. Second, the novel technique of using ground based measurements of vibration of the orbiting satellite was employed. The LACE has a heavy central body to which is attached booms with lengths as long as 150 feet. The ground measurements were obtained using laser Doppler radar at the MIT Lincoln Laboratory Firepond Facility. The initial tests demonstrated the accuracy of the vibration measurements and obtained structural responses for enhancing the accuracy of the mathematical model of the structural dynamics. Germanium corner-cube retroreflectors attached to the central body and a boom deployed to 18 feet ensured a high strength return signal. Subsequent tests demonstrated the ability of an open-loop damper to attenuate the vibrations of the orbiting satellite. The LACE test results are important in contributing to the validation of a CSI technique, and demonstrating a novel ground measurement technique for orbital tests that is accurate but which has very low cost

The reduced order model problem in distributed parameter systems adaptive identification and control

The basic assumption that a large space structure can be decoupled preceding the application of reduced order active control was considered and alternative solutions to the control of such structures (in contrast to the strict modal control) were investigated. The transfer function matrix from the actuators to the sensors was deemed to be a reasonable candidate. More refined models from multivariable systems theory were studied and recent results in the multivariable control field were compared with respect to theoretical deficiencies and likely problems in application to large space structures