Naval Information Warfare Center Pacific

Abstract Telework has inspired research in disciplines ranging from transportation and urban planning to ethics, law, sociology, and organizational studies. In our review of this literature, we seek answers to three questions: who participates in telework, why they do, and what happens when they do? Who teleworks remains elusive, but research suggests that male professionals and female clerical workers predominate. Notably, work‐related factors like managers' willingness are most predictive of which employees will telework. Employees' motivations for teleworking are also unclear, as commonly perceived reasons such as commute reduction and family obligations do not appear instrumental. On the firms' side, managers' reluctance, forged by concerns about cost and control and bolstered by little perceived need, inhibits the creation of telework programmes. As for outcomes, little clear evidence exists that telework increases job satisfaction and productivity, as it is often asserted to do. We suggest three steps for future research may provide richer insights: consider group and organizational level impacts to understand who telework affects, reconsider why people telework, and emphasize theory‐building and links to existing organizational theories. We conclude with lessons learned from the telework literature that may be relevant to research on new work forms and workplaces. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract This study employs a grounded theory methodology to compare the impact telecommuting has on public and private employees perceptions of professional isolation. It relied on 93 semi‐structured interviews with telecommuters, non‐telecommuters, and their respective supervisors in two high technology firms and two city governments. These organizations had active telecommuting programmes and a strong interest in making telecommuting a successful work option, providing an opportunity to investigate the challenges of telecommuting that existed even within friendly environments. The interviews demonstrated that professional isolation of telecommuters is inextricably linked to employee development activities (interpersonal networking, informal learning, and mentoring). The extent to which telecommuters experience professional isolation depends upon the extent to which these activities are valued in the workplace and the degree to which telecommuters miss these opportunities. Public respondents appeared to value these informal developmental activities less than private employees. Therefore, we stipulate that telecommuting is less likely to hinder the professional development of public sector employees than that of employees in the private sector. Copyright © 2002 John Wiley & Sons, Ltd.

Reliable estimation of the size or density of wild animal populations is very important for effective wildlife management, conservation and ecology. Currently, the most widely used methods for obtaining such estimates involve either sighting animals from transect lines or some form of capture-recapture on marked or uniquely identifiable individuals. However, many species are difficult to sight, and cannot be easily marked or recaptured. Some of these species produce readily identifiable sounds, providing an opportunity to use passive acoustic data to estimate animal density. In addition, even for species for which other visually based methods are feasible, passive acoustic methods offer the potential for greater detection ranges in some environments (e.g. underwater or in dense forest), and hence potentially better precision. Automated data collection means that surveys can take place at times and in places where it would be too expensive or dangerous to send human observers. Here, we present an overview of animal density estimation using passive acoustic data, a relatively new and fast-developing field. We review the types of data and methodological approaches currently available to researchers and we provide a framework for acoustics-based density estimation, illustrated with examples from real-world case studies. We mention moving sensor platforms (e.g. towed acoustics), but then focus on methods involving sensors at fixed locations, particularly hydrophones to survey marine mammals, as acoustic-based density estimation research to date has been concentrated in this area. Primary among these are methods based on distance sampling and spatially explicit capture-recapture. The methods are also applicable to other aquatic and terrestrial sound-producing taxa. We conclude that, despite being in its infancy, density estimation based on passive acoustic data likely will become an important method for surveying a number of diverse taxa, such as sea mammals, fish, birds, amphibians, and insects, especially in situations where inferences are required over long periods of time. There is considerable work ahead, with several potentially fruitful research areas, including the development of (i) hardware and software for data acquisition, (ii) efficient, calibrated, automated detection and classification systems, and (iii) statistical approaches optimized for this application. Further, survey design will need to be developed, and research is needed on the acoustic behaviour of target species. Fundamental research on vocalization rates and group sizes, and the relation between these and other factors such as season or behaviour state, is critical. Evaluation of the methods under known density scenarios will be important for empirically validating the approaches presented here.

We develop anomaly detectors, i.e., detectors that do not presuppose a signature model of one or more dimensions, for three clutter models: the local normal model, the global normal mixture model, and the global linear mixture model. The local normal model treats the neighborhood of a pixel as having a normal probability distribution. The normal mixture model considers the observation from each pixel as arising from one of several possible classes such that each class has a normal probability distribution. The linear mixture model considers each observation to be a linear combination of fixed spectra, known as endmembers, that are, or may be, associated with materials in the scene, and the coefficients, interpreted as fractional abundance, are constrained to be nonnegative and sum to one. We show how the generalized likelihood ratio test (GLRT) may be used to derive anomaly detectors for the local normal and global normal mixture models. The anomaly detector applied with the linear mixture approach proceeds by identifying target like endmembers based on properties of the histogram of the abundance estimates and employing a matched filter in the space of abundance estimates. To overcome the limitations of the individual models, we develop a joint decision logic, based on a maximum entropy probability model and the GLRT, that utilizes multiple decision statistics, and we apply this approach using the detection statistics derived from the three clutter models. Examples demonstrate that the joint decision logic can improve detection performance in comparison with the individual anomaly detectors. We also describe the application of linear prediction filters to repeated images of the same area to detect changes that occur within the scene over time.

(2008). MARINE MAMMAL NOISE-EXPOSURE CRITERIA: INITIAL SCIENTIFIC RECOMMENDATIONS. Bioacoustics: Vol. 17, No. 1-3, pp. 273-275.

We discuss distributed denial of service attacks in the Internet. We were motivated by the widely known February 2000 distributed attacks on Yahoo!, Amazon.com, CNN.com, and other major Web sites. A denial of service is characterized by an explicit attempt by an attacker to prevent legitimate users from using resources. An attacker may attempt to: "flood" a network and thus reduce a legitimate user's bandwidth, prevent access to a service, or disrupt service to a specific system or a user. We describe methods and techniques used in denial of service attacks, and we list possible defences. In our study, we simulate a distributed denial of service attack using ns-2 network simulator. We examine how various queuing algorithms implemented in a network router perform during an attack, and whether legitimate users can obtain desired bandwidth. We find that under persistent denial of service attacks, class based queuing algorithms can guarantee bandwidth for certain classes of input flows.

This review considers the effect of anthropogenic sound on beaked whales2. Two major conclusions are presented: (1) gas-bubble disease, induced in supersaturated tissue by a behavioural response to acoustic exposure, is a plausible pathologic mechanism for the morbidity and mortality seen in cetaceans associated with sonar exposure and merits further investigation; and (2) current monitoring and mitigation methods for beaked whales are ineffective for detecting these animals and protecting them from adverse sound exposure. In addition, four major research priorities, needed to address information gaps on the impacts of sound on beaked whales, are identified: (1) controlled exposure experiments to assess beaked whale responses to known sound stimuli; (2) investigation of physiology, anatomy, pathobiology and behaviour of beaked whales; (3) assessment of baseline diving behaviour and physiology of beaked whales; and (4) a retrospective review of beaked whale strandings.

Beaked whales have mass stranded during some naval sonar exercises, but the cause is unknown. They are difficult to sight but can reliably be detected by listening for echolocation clicks produced during deep foraging dives. Listening for these clicks, we documented Blainville's beaked whales, Mesoplodon densirostris, in a naval underwater range where sonars are in regular use near Andros Island, Bahamas. An array of bottom-mounted hydrophones can detect beaked whales when they click anywhere within the range. We used two complementary methods to investigate behavioral responses of beaked whales to sonar: an opportunistic approach that monitored whale responses to multi-day naval exercises involving tactical mid-frequency sonars, and an experimental approach using playbacks of simulated sonar and control sounds to whales tagged with a device that records sound, movement, and orientation. Here we show that in both exposure conditions beaked whales stopped echolocating during deep foraging dives and moved away. During actual sonar exercises, beaked whales were primarily detected near the periphery of the range, on average 16 km away from the sonar transmissions. Once the exercise stopped, beaked whales gradually filled in the center of the range over 2-3 days. A satellite tagged whale moved outside the range during an exercise, returning over 2-3 days post-exercise. The experimental approach used tags to measure acoustic exposure and behavioral reactions of beaked whales to one controlled exposure each of simulated military sonar, killer whale calls, and band-limited noise. The beaked whales reacted to these three sound playbacks at sound pressure levels below 142 dB re 1 µPa by stopping echolocation followed by unusually long and slow ascents from their foraging dives. The combined results indicate similar disruption of foraging behavior and avoidance by beaked whales in the two different contexts, at exposures well below those used by regulators to define disturbance.

Airborne mineral dust can impact visibility, climate, biogeochemical processes, and possibly human health. The magnitude of the impact of dust depends on particle size. We measured the size distributions of airborne mineral dust over the Canary Islands during July 1995 and Puerto Rico during July 2000. Dust size distributions do not appear lognormal. Stokes gravitational settling overestimates losses of large dust particles during atmospheric transport from North Africa over the tropical North Atlantic and Caribbean. Normalized mineral dust size distributions of particles smaller than 7.3 μm over the Canary Islands and Puerto Rico were indistinguishable, indicating these particles were not preferentially removed during atmospheric transport. However, mineral dust aerosols larger than 7.3 μm were preferentially removed during atmospheric transport. Larger particles were more efficiently removed. A simple empirical model setting the vertical velocity of dust particles equal to the Stokes gravitational settling velocity minus an upward velocity of ∼0.33 cm s −1 accurately predicts changes in dust size distribution during atmospheric transport. Thus it appears some atmospheric process(es) partially counteracts gravitational settling.

This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) with six degrees of freedom. We approach this problem using an error state formulation of the Kalman filter. Integration of the vehicle's high-rate inertial measurement unit's (IMU's) accelerometers and gyros allow time propagation while other sensors provide measurement corrections. The low-rate aiding sensors include a Doppler velocity log (DVL), an acoustic long baseline (LBL) system that provides round-trip travel times from known locations, a pressure sensor for aiding depth, and an attitude sensor. Measurements correct the filter independently as they arrive, and as such, the filter is not dependent on the arrival of any particular measurement. We propose novel tightly coupled techniques for the incorporation of the LBL and DVL measurements. In particular, the LBL correction properly accounts for the error state throughout the measurement cycle via the state transition matrix. Alternate tightly coupled approaches ignore the error state, utilizing only the navigation state to account for the physical latencies in the measurement cycle. These approaches account for neither the uncertainty of vehicle trajectory between interrogation and reply, nor the error state at interrogation. The navigation system also estimates critical sensor calibration parameters to improve performance. The result is a robust navigation system. Simulation and experimental results are provided.

Ecologists who specialize in translational ecology ( TE ) seek to link ecological knowledge to decision making by integrating ecological science with the full complement of social dimensions that underlie today's complex environmental issues. TE is motivated by a search for outcomes that directly serve the needs of natural resource managers and decision makers. This objective distinguishes it from both basic and applied ecological research and, as a practice, it deliberately extends research beyond theory or opportunistic applications. TE is uniquely positioned to address complex issues through interdisciplinary team approaches and integrated scientist–practitioner partnerships. The creativity and context‐specific knowledge of resource managers, practitioners, and decision makers inform and enrich the scientific process and help shape use‐driven, actionable science. Moreover, addressing research questions that arise from on‐the‐ground management issues – as opposed to the top‐down or expert‐oriented perspectives of traditional science – can foster the high levels of trust and commitment that are critical for long‐term, sustained engagement between partners.

During the last half century, identification of an ideal (predominantly entropic) protein elastomer was generally thought to require that the ideal protein elastomer be a random chain network. Here, we report two new sets of data and review previous data. The first set of new data utilizes atomic force microscopy to report single-chain force-extension curves for (GVGVP)(251) and (GVGIP)(260), and provides evidence for single-chain ideal elasticity. The second class of new data provides a direct contrast between low-frequency sound absorption (0.1-10 kHz) exhibited by random-chain network elastomers and by elastin protein-based polymers. Earlier composition, dielectric relaxation (1-1000 MHz), thermoelasticity, molecular mechanics and dynamics calculations and thermodynamic and statistical mechanical analyses are presented, that combine with the new data to contrast with random-chain network rubbers and to detail the presence of regular non-random structural elements of the elastin-based systems that lose entropic elastomeric force upon thermal denaturation. The data and analyses affirm an earlier contrary argument that components of elastin, the elastic protein of the mammalian elastic fibre, and purified elastin fibre itself contain dynamic, non-random, regularly repeating structures that exhibit dominantly entropic elasticity by means of a damping of internal chain dynamics on extension.

This paper describes a transformation technique aimed at solving the peak-to-average power ratio (PAPR) problem associated with OFDM (orthogonal frequency-division multiplexing). Constant envelope OFDM (CE-OFDM) transforms the OFDM signal, by way of phase modulation, to a signal designed for efficient power amplification. At the receiver, the inverse transformation - phase demodulation - is applied prior to the conventional OFDM demodulator. The performance of CE-OFDM is analyzed in additive white Gaussian noise (AWGN) and fading channels. CE-OFDM is shown to achieve good performance in dense multipath with the use of cyclic prefix transmission in conjunction with a frequency- domain equalizer (FDE). By way of computer simulation and hardware realization, CE-OFDM is shown to compare favorably to conventional OFDM.

Marine mammals play crucial ecological roles in the oceans, but little is known about their microbiotas. Here we study the bacterial communities in 337 samples from 5 body sites in 48 healthy dolphins and 18 healthy sea lions, as well as those of adjacent seawater and other hosts. The bacterial taxonomic compositions are distinct from those of other mammals, dietary fish and seawater, are highly diverse and vary according to body site and host species. Dolphins harbour 30 bacterial phyla, with 25 of them in the mouth, several abundant but poorly characterized Tenericutes species in gastric fluid and a surprisingly paucity of Bacteroidetes in distal gut. About 70% of near-full length bacterial 16S ribosomal RNA sequences from dolphins are unique. Host habitat, diet and phylogeny all contribute to variation in marine mammal distal gut microbiota composition. Our findings help elucidate the factors structuring marine mammal microbiotas and may enhance monitoring of marine mammal health.

Underwater acoustic networks are generally formed by acoustically connected ocean bottom sensor nodes, autonomous underwater vehicles (AUVs), and surface stations that serve as gateways and provide radio communication links to on-shore stations. The quality of service of such networks is limited by the low bandwidth of acoustic transmission channels, high latency resulting from the slow propagation of sound, and elevated noise levels in some environments. The long-term goal in the design of underwater acoustic networks is to provide for a self-configuring network of distributed nodes with network links that automatically adapt to the environment through selection of the optimum system parameters. This article considers several aspects in the design of shallow water acoustic networks that maximize throughput and reliability while minimizing power consumption.

The theoretical limit for small antenna performance that was derived decades ago by Wheeler and Chu governs design tradeoffs for size, bandwidth, and efficiency. Theoretical guidelines have also been derived for other details of small antenna design such as permittivity, aspect ratio, and even the nature of the internal structure of the antenna. In this paper, we extract and analyze experimental performance data from a large body of published designs to establish several facts that have not previously been demonstrated: (1) The theoretical performance limit for size, bandwidth, and efficiency are validated by all available experimental evidence. (2) Although derived for electrically small antennas, the same theoretical limit is also generally a good design rule for antennas that are not electrically small. (3) The theoretical predictions for the performance due to design factors such as permittivity, aspect ratio, and the internal structure of the antenna are also supported by the experimental evidence. The designs that have the highest performance are those that involve the lowest permittivity, have an aspect ratio close to unity, and for which the fields fill the minimum size enclosing sphere with the greatest uniformity. This work thus validates the established theoretical design guidelines.

This paper presents a behavior-based adaptive mission planner (AMP)to trace a chemical plume to its source and reliably declare the source location. The proposed AMP is implemented on a REMUS autonomous underwater vehicle (AUV)equipped with multiple types of sensors that measure chemical concentration,the flow velocity vector, and AUV position, depth, altitude, attitude, and speed. This paper describes the methods and results from experiments conducted in November 2002 on San Clemente Island, CA, using a plume of Rhodamine dye developed in a turbulent fluid flow (i.e., near-shore ocean conditions). These experiments demonstrated chemical plume tracing over 100 m and source declaration accuracy relative to the nominal source location on the order of tens of meters. The designed maneuvers are divided into four behavior types: finding a plume,tracing the plume, reacquiring the plume, and declaring the source location. The tracing and reacquiring behaviors are inspired by male moths flying up wind along a pheromone plume to locate a sexually receptive female. All behaviors are formulated by perception and action modules and translated into chemical plume-tracing algorithms suitable for implementation on a REMUS AUV. To coordinate the different behaviors, the subsumption architecture is adopted to define and arbitrate the behavior priorities. AUVs capable of such feats would have applicability in searching for environmentally interesting phenomena, unexploded ordnance, undersea wreckage, and sources of hazardous chemicals or pollutants.

Abstract Condensations between 3‐X‐2,4‐dimethylpyrroles (X = H, CH 3 , C 2 H 5 , and CO 2 C 2 H 5 ) and acyl chlorides gave derivatives of 3,5,3′,5′‐tetramethylpyrromethene (isolated as their hydrochloride salts): 6‐methyl, 6‐ethyl, 4,4′,6‐trimethyl, 4,4′‐diethyl‐6‐methyl, and 4,4′‐dicarboethoxy‐6‐ethyl derivatives for conversion on treatment with boron trifluoride to 1,3,5,7‐tetramethylpyrromethene–BF 2 complex (TMP–BF 2 ) and its 8‐methyl (PMP–BF 2 ), 8‐ethyl, 2,6,8‐trimethyl (HMP–BF 2 ),2,6,‐diethyl‐8‐methyl (PMDEP–BF 2 ), and 2,6‐dicarboethoxy‐8‐ethyl derivatives. Chlorosulfonation converted, 1,3,5,7,8‐pentamethylpyrromethene–BF 2 complex to its 2,6‐disulfonic acid isolated as the lithium, sodium (PMPDS–BF 2 ), potassium, rubidium, cesium, ammonium, and tetramethylammonium disulfonate salts and the methyl disulfonate ester. Sodium 1,3,5,7‐tetramethyl‐8‐ethylpyrromethene‐2,6‐disulfonate–BF 2 complex was obtained from the 8‐ethyl derivative of TMP–BF 2 . Nitration and bromination converted PMP–BF 2 to its 2,6‐dinitro‐(PMDNP–BF 2 ) and 2,6‐dibromo‐ derivatives. The time required for loss of fluorescence by irradiation from a sunlamp showed the following order for P–BF 2 compounds (10 −3 to 10 −4 M) in ethanol: PMPDS–BF 2 , 7 weeks; PMP–BF 2 , 5 days; PMDNP–BF 2 , 72 h; HMP–BF 2 , 70 h; and PMDEP–BF 2 , 65 h. Under similar irradiation PMPDS–BF 2 in water lost fluorescence after 55 h. The dibromo derivative was inactive, but each of the other pyrromethene–BF 2 complexes under flashlamp excitation showed broadband laser activity in the region λ 530–580 nm. In methanol PMPDS–BF 2 was six times more resistant to degradation by flashlamp pulses than was observed for Rhodamine‐6G (R‐6G). An improvement (up to 66%) in the laser power efficiency of PMPDS–BF 2 (10 −4 M in methanol) in the presence of caffeine (a filter for light <300 nm) was dependent on flashlamp pulse width (2.0 to 7.0 μsec).

Abstract Research into dolphin swimming has historically been guided by false assumptions of ‘effortless’, ‘high‐speed’ swimming. These assumptions have instigated the development of drag‐reduction hypotheses but tests of these hypotheses have generally had little success. The autecological approach has dominated recent efforts and has been more successful. In this review we summarize results of decades of research efforts to study these creatures. (1) Drag is minimized primarily by the streamlined shape of the body and appendages, with no known contributions from compliant dampening, dermal ridges, secretions, boundary layer heating, or skin folds. All indications are that the boundary layer is turbulent. (2) Muscles for the upstroke and downstroke of swimming dolphins provide approximately equal power. (3) Output force is enhanced by insertions occurring on the long processes of the vertebrae and on the subdermal connective tissue sheath. (4) Measured swimming speeds are lower than previously believed, with maximum reported routine speeds being approximately 3 m/s. (5) Porpoising behaviour appears to be the most energetically conservative manner in which to breathe when swimming at high speed. (6) Riding surf and wind waves involves the balance between the wave slope and the weight of the animal whereas riding the bow wave involves the interaction of the pressure wave in front of a ship and the drag of the dolphin.

Hysteresis measurements have become an important part of characterizing magnetic behavior of rocks in paleomagnetic studies. Theoretical interpretation is often difficult owing to the complexity of mineral magnetism and published data sets demonstrate remanence and coercivity behavior that is currently unexplained. In the last decade, numerical micromagnetic modeling has been used to simulate magnetic particles. Such simulations reveal the existence of nonuniform remanent states between single and multidomain, known as the “flower” and “vortex” configurations. These suggest plausible explanations for many hysteresis measurements yet fall short of explaining high saturation remanence, high coercivity data such as those commonly observed in fine grained submarine basalts. In this paper, we review the theoretical and experimental progress to date in understanding hysteresis of geological materials. We extend numerical simulations to a greater variety of shapes and sizes, including random assemblages of particles and shapes more complex than simple rods and cubes. Our simulations provide plausible explanations for a wide range of hysteresis behavior.