Defense Technical Information Center

A new technique for determining the terminal reliability of probabilistic networks is derived and discussed. The technique uses set-theoretic concepts to partition the space of all graph realizations in a way which permits extremely fast evaluation of the source-to-terminal probability. If not allowed to run to completion, the algorithm yields rapidly converging upper and lower bounds on that probability. Comparison with algorithms in the recent literature shows a decrease of one or two orders of magnitude in required CPU time.

properties in the longitudinal (all weld metal) orientation differed significantly from those in the transverse (composite) orientation; the longitudinal orientation had superior creep-rupture properties. This was partly because the transverse (composite) weldment contained some weaker base metal. A creep law was developed to represent the strain-time behavior of the longitudinal weld metal specimens for times to 36 Ms (10,000 h).

Results are developed for data traffic performance in an integrated multiplex structure which includes circuit-switching for voice and packet-switching for data. The results are obtained both through simulation and analysis, and show that excessive data queues and delays will build up under heavy loading conditions. These large data delays occur during periods of time when the voice traffic load through the multiplexer exceeds its statistical average. A variety of flow control mechanisms to reduce data packet delays are investigated. These mechanisms include control of voice bit rate, limitation of the data buffer, and combinations of voice rate and data buffer control. Simulations indicate that these flow control mechanisms provide substantial improvements in system performance.

A constitutive theory for use in high-temperature structural analysis of breeder reactor components is presented. It is unified in the sense that plastic and creep strains are considered to arise from similar physical mechanisms. The theory is presented in multiaxial terms along with a discussion of its underlying assumptions, its relationship to other theories and the experimental observations upon which it is based and is intended to model. The results of an extensive parameter sensitivity study are reported which provide understanding of the influence of the various model parameters on the critical features of predicted response.

Results are shown graphically and show the source data on which the approximations are based in addition to some results from other complications for comparison.

The familiar Lanchester square law attrition model assumes that the attrition produced by a force is independent of enemy force size. This assumption may require modification if the larger force suffers inefficiencies of scale when force sizes are grossly unequal. A modification that alters relative force attrition capability by a factor depending on the force ratio is introduced and discussed in terms of a special case.

This symposium addresses the complications encountered by medical planners when confronted by the use or threat of the use of weapons of mass destruction. The types of chemical warfare agents (CWA), their principal target organs, and physiological effects are discussed. We have reviewed the use of CWA in 20th century warfare and otherwise with emphasis on five cases: (1) use of sulfur mustard during World War I; (2) use by Italy against Ethiopia; (3) use in the Sino-Japanese War; (4) relatively well-studied use in the Iran-Iraq conflict; and (5) the use of sarin in the Tokyo subway terrorist incident. We reviewed the additional physiological and psychological consequences of their use and threat of use. Results from training and simulation are discussed. Finally, we present our conclusions derived from the analysis of these historical situations.

Wet deposition, including both in- and below-cloud scavenging, is critical for the atmospheric transport modeling of 137Cs following the Fukushima Daiichi Nuclear power plant (FDNPP) accident. Although intensively investigated, wet deposition simulation is still subject to uncertainties of meteorological inputs and wet scavenging modeling, leading to biased 137Cs transport prediction. To reduce the dual uncertainties, in- and below-cloud wet scavenging schemes of 137Cs were simultaneously integrated into Weather Research and Forecasting-Chemistry (WRF-Chem), yielding online coupled modeling of meteorology and the two wet scavenging processes. The integration was performed using 25 combinations of different in- and below-cloud schemes, covering most schemes in the literature. Two microphysics schemes were also tested to better reproduce the precipitation. The 25 models and the ensemble mean of 9 representative models were systematically compared with the below-cloud-only WRF-Chem model, using the cumulative deposition and atmospheric concentrations of 137Cs measurements. The results reveal that, with the Morrison's double moment cloud microphysics scheme, the developed models could better reproduce the rainfall and substantially improve the cumulative deposition simulation. The in-cloud scheme is influential to the model behaviors and those schemes considering cloud parameters also improve the atmospheric concentration simulations, whereas the others solely dependent on the rain intensity are sensitive to meteorology. The ensemble mean achieves satisfactory performance except one plume event, but still outperforms most models.

The paper presents a near-optimal guidance law that has been developed using the direct method of calculus of variations. By the direct access to controlling the shape of the trajectory, this guidance law seeks to maximize the kinetic energy transfer upon interception from a surface launched medium range interceptor missile to a ballistic missile target during the boost phase of flight. Mathematical models of a two-stage liquid-fueled medium-range ballistic missile and a velocity-limited endoatmospheric interceptor missile with onboard active radar guidance are used to demonstrate the guidance law’s performance. This law will utilize the interceptor's onboard computer and active radar sensors to independently predict an intercept point, solve the two-point boundary-value problem, and determine the best feasible flight path to that point. While determining a truly optimal flight path would require significant computing power and therefore cannot be realized online, the proposed nearoptimal flight path can be calculated onboard the interceptor in fractions of a second and updated in multiple times during the intercept without significant technological advancements in the interceptor’s onboard hardware. That near-optimal guidance path is then converted into a set of command functions and fed back into the control system of the interceptor. By modifying just a few parameters affecting the higher-order derivatives at the intercept point, the optimization algorithm varies the shape of a three-dimensional trajectory over a wide range without compromising the constraints on controls or jeopardizing satisfaction of the final conditions. An example features the guidance solution for probably the most difficult scenario of maximizing kinetic energy upon impact by forcing it to occur at a right angle.

Rationale: Public health and preventive medicine (PHPM) has been recognized internationally as a physician specialty, but national parallels and differences exist between training contexts. This paper reviews PHPM training and employment in Canada, France, Italy, Japan, the United Kingdom, and the USA.Methods: Information gathered from relevant accreditation bodies and literature searches was used to create descriptive profiles of national training demographics and structure and a narrative outlining trends and challenges facing the specialty.Results: Notable similarities and differences exist between national contexts. Key themes were differences in training strategies and practice scope, specialty stakeholders, certification structure, and funding. Recognition challenges faced the specialty across all six countries. Other challenges included unclear competencies and training strategies and a need for PHPM specialists to highlight their role in combating population health threats. Additional differences existed between comparator countries on the structure of training, funding sources for training programs, availability of training posts, and linkages with other physician specialties.Conclusion: Highlighting these themes is a first step to fostering training collaborations between PHPM specialist physicians to augment transnational action on global public health challenges and also supports PHPM physician educators with innovative solutions from abroad that might address domestic specialty challenges.

We develop a mathematical analysis for the steady state performance of a system where voice calls and data packets are transmitted over the same channel. The voice calls have priority over the data packets, in that the data packets are transmitted only when there are no voice calls present in the system or the voice conversation is in a long silent period.

Abstract In an integrated telecommunications network, voice and data traffic compete for the same transmission facilities. Assuming Poisson arrivals and exponential service with different rates, analytic expressions are obtained for measures of performance such as blocking probability and average delay under the following operating rule: class 1 traffic behaves as a loss system while class 2 traffic is buffered when all channels are busy. In view of the inordinate amount of computational effort needed when the number of channels is large, simple approximations have been suggested.

Queueing systems with interruptions serve as models for a variety of situations occurring in every day life. Usually, for each type of interruption, a separate queueing analysis is required. In this paper we present a single queueing model which can be used to analyze many such systems. The model is in the form of an approximation that is based upon several parameters, which reflect the particular queueing system under consideration. Applications to queueing systems with priorities and breakdowns are given in the paper.

F OR many years now, the U.S. Department of Defense has expended great effort to develop an integrated intercontinental ballistic missile (ICBM) defense system through a layered, defense in depth strategy. An ICBM’s speed and altitude leave little room for error by the defender, and any strategy must include systems capable of defeating a ballisticmissile (BM) at each of its three distinct phases (boost, midcourse, and terminal), which theMissile Defense Agency labels the engagement sequence groups (ESG) [1]. It is the portion of the effort directed toward the boost phase of the Ballistic Missile Defense Programs that is the focus of this Note. The boost-phase ESG is concerned with developing methods and technologies to conduct boost-phase intercept (BPI). Intercepting a missile in its boost phase is the ideal solution for a ballistic missile defense, because the missile is very vulnerable during this phase of its flight. The missile is relatively slow while struggling to overcome gravity, has a very visible exhaust plume, and cannot deploy countermeasures. Yet, the challenges that need to be overcome are immense: countering the large and changing acceleration rates, reliable scanning and tracking, and very short reaction time are among the most daunting. A variety of weapon systems are under development for conducting BPI, including airborne lasers, spacebased intercept missiles, and ground-based intercept missiles. None of these systems is totally operational, though several look promising [1–3]. A missile’s guidance law is one of the largest single factors affecting its ability to intercept a target. Yet,when discussingmission success in the BPI ESG, intercepting the target is only one factor; another major consideration is the ability to kill the target, using the available kinetic energy as effectively as possible. This suggests the need to control the geometry of the interception [4]. The discussion of the existing approaches aswell as the genericmodels of ICBMand interceptor used in this study can be found in [5]. One of the findings of that paper is the constraint on the intercept altitude. As is well known, an endoatmospheric missile has a hard time maneuvering at high altitudes due to the low density of the surrounding atmosphere. Thus, the maximum allowable intercept value of 50–60 km is considered as the upper limit. The BM thrust model assuming the sharp drops at 130 and 240 s to represent the staging events suggests that 50–60-km altitude will be achieved between 130 and 140 s [5]. This is one of the most significant limitations on the BPI problem, because any station activelymonitoring the launch areawill still need 45–60 s to detect, track, analyze, and engage the target [3]. In the current study, simulations assume a 60-s delay in the interceptor launch, leaving about only 70–80 s for intercept per se. This Note does not address the question of achieving operationability for various engagement scenarios, but rather offers an approach to rapidly compute intercept trajectories in case it is possible in principle. To this end, Sec. II develops and describes the essence of a new direct-method-based guidance law continuously calculated onboard the missile as a complete solution of a two-point boundary-value problem (TPBVP), and Sec. III presents some simulation results and discusses the feasibility of employing the proposed guidance law in the real-world conditions.

As an essential ingredient of Internet of Things (IoT), IPv6-based Low Power and Lossy Networks (LLNs) largely consisting of various resource-constrained devices are expeditiously proliferating and playing an important role in the realization of ubiquitous computing and communication infrastructure. In order to provide efficient and reliable communication between resource-constrained devices and connect them to the Internet, a novel routing protocol for LLNs, a.k.a. RPL, has been proposed. However, due to wide distribution, openness, and instinctive resource constraints of IoT devices, IoT and its applications become an ideal target for cyber attacks. Thus, investigating potential attacks against IoT-related routing protocol is a top priority to improve the security of the future IoT systems. In this paper, we propose a Gini index-based countermeasure to effectively detect and mitigate sybil attack in RPL- based LLNs, where the malicious node multicasts an excessive number of DODAG Information Solicitation (DIS) messages with different fictitious identities to cause the legitimate nodes to restart the Trickle algorithm frequently and broadcast a large number of DODAG Information Object (DIO) messages to quickly drain the limited energy resource of legitimate nodes. We conduct extensive simulation experiments for performance evaluation and comparison using OMNeT++, and the simulation results show that the proposed countermeasure can accurately detect and effectively mitigate sybil attack, indicating a viable approach against cyber attack in the Internet of Things.

Techniques for obtaining optimum timekeeping performance from precision station clocks are presented. Kalman filters and ARIMA models are used to study the predictability of precision clocks based on quartz, rubidium and cesium technology. The software performing the time prediction error analysis utilizes either Kalman filters or ARIMA models to estimate the time, frequency, and frequency aging of a clock over an initial calibration interval. Forecasts for intervals from one minute up to one year are given. The forecasts are compared to the actual time of the clock to determine the forecast error. After the RMS forecast error is updated for each interval, the starting point is advanced and the process is repeated. This technique is used to study the performance of thirteen clocks over a two year time period. Adaptive versions of both the ARIMA and Kalman approaches which were developed using real-time estimators of the filter/model parameters are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The National Science and Technology Council, within the Executive Office of the President, established the Pandemic Prediction and Forecasting Science and Technology Working Group in 2013 to advance US Government epidemic prediction and forecasting capabilities. Working Group leaders will provide an overview of activities, and seek feedback on the Working Group direction from the ISDS community.

Abstract In the study of complex queueing systems, analysis techniques aimed al providing exact solutions become ineffective. Approximation techniques provide an attractive alternative in such cases. This paper gives an overview of different types of approximation techniques available in the literature and points out their relative merits. Also, the need for proper validation procedures of approximation techniques is emphasized.

When you travel abroad it is very likely the electrical appliances used at home will not work when you get to your destination. The standard plugs you use at home are not the standard used at the location you are visiting. Standards, although important, do not assure interoperability. More to the point of interest to the scientific, technical, and medical information community interoperability does not assure access to sources of knowledge. “In paper-based publication of scientific and technical reports, interoperability, except for language differences and visual challenges, is achieved through a single publication medium. In the digital environment with its multiple types of media, even defining the concept of publishing is a challenge” [1]. User behavior is changing with a growing requirement to link text and data resources. Sometimes, in the rush to do things, we simply forget the obvious. This particularly is true when a large cultural change is upon us. During the 5000 years since the development of writing, humankind continually has improved ways to store, organize and transfer our knowledge in physical containers such as tablets, books, newspapers, and journals. Ten years ago, when an easy to use Web browser became available on the Internet, the world suddenly began a massive change. A change lacking many of the library and other information discovery standards developed and instituted over centuries. A change, however, that would not have occurred without technology standards. Historically, the range of hardware, software, and platform products from different vendors made it difficult or impossible for to share data and information effectively because, by and large, they were (and still are) designed to permit interoperability among computer hardware and software components. Information technology standards are critical components to make seamless access a reality. However, all elements of the information continuum must allow universal interoperability. The value of knowledge can be realized only when it is disseminated and shared – and used – throughout the information continuum. Generally the term information continuum is used to describe the whole set of all needed information, from origin through archival access. Currently, and in the foreseeable future there is no set of standards that can apply throughout the continuum. Recognizing the need many governments, often under the rubric of e-Government, are publishing interoperability frameworks with accompanying standards. The basic intent for these and other governmental efforts is to allow information to flow seamlessly across the public sector and provide citizens and business with better access to government services. To name a few, in the United States it is the Federal Enterprise Architecture (FEA), in the United Kingdom, New Zealand, Denmark and others it is the Egovernment Interoperability Framework (e-GIF), and in France it is the French ‘common interoperability framework’ (CCI). The European Interoperability Framework document “provides recommendations

In an integrated telecommunications system both voice and data compete for use of the same group of channels. Such a system allows for better use of the channels and more efficient use of the system facilities. Numerous operating rules for allowing voice and data access to the channels can be considered. In this paper, we give a steady state queueing analysis for two priority rules, voice pre-empting data and data pre-empting voice, when the mean service times of voice and data are different.