Carl Jensen

Passive acoustic mapping utilizing optimal beamforming in ultrasound therapy monitoring.

Passive acoustic mapping (PAM) is a promising imaging method that enables real-time three-dimensional monitoring of ultrasound therapy through the reconstruction of acoustic emissions passively received on an array of ultrasonic sensors. A passive beamforming method is presented that provides greatly improved spatial accuracy over the conventionally used time exposure acoustics (TEA) PAM reconstruction algorithm. Both the Capon beamformer and the robust Capon beamformer (RCB) for PAM are suggested as methods to reduce interference artifacts and improve resolution, which has been one of the experimental issues previously observed with TEA. Simulation results that replicate the experimental artifacts are shown to suggest that bubble interactions are the chief cause. Analysis is provided to show that these multiple bubble artifacts are generally not reduced by TEA, while Capon-based methods are able to reduce the artifacts. This is followed by experimental results from in vitro experiments and in vivo oncolytic viral therapy trials that show improved results in PAM, where RCB is able to more accurately localize the acoustic activity than TEA.

Thermoacoustic power conversion using a piezoelectric transducera)

The predicted efficiency of a simple thermoacoustic waste heat power conversion device has been investigated as part of a collaborative effort combining a thermoacoustic engine with a piezoelectric transducer. Symko et al. [Microelectron. J. 35, 185-191 (2004)] at the University of Utah built high frequency demonstration engines for this application, and Lynn [ASMDC report, accession number ADA491030 (2008)] at the University of Washington designed and built a high efficiency piezoelectric unimorph transducer for electroacoustic conversion. The design presented in this paper is put forward to investigate the potential of a simple high frequency, air filled, standing wave thermoacoustic device to be competitive with other small generator technologies such as thermoelectric devices. The thermoacoustic generator is simulated using a low-amplitude approximation for thermoacoustics and the acoustic impedance of the transducer is modeled using an equivalent circuit model calculated from the transducers mechanical and electrical properties. The calculations demonstrate that a device performance of around 10% of Carnot efficiency could be expected from the design which is competitive with currently available thermoelectric generators.

Beyond the Tea Leaves Futures Research and Terrorism

No one can predict the future. The study of futures research, however, offers insights that may assist in foreseeing certain trends that will affect future events. This article employs a modified version of one futures research methodology, cross-impact analysis, to study the interactions of four trends that will likely influence the future of international terrorism: the expanded use of the Internet on the international level, the effects of emerging ethnic and religious sensibilities, the growing economic gap between the rich and the poor, and the continued role of the United States as the worlds predominant superpower.

Thermoacoustic properties of fibrous materials

The thermoacoustic properties of fibrous materials are studied using a computational fluid simulation as a test of proposed analytical models for propagation in porous materials with an ambient temperature gradient. The acoustic properties of porous materials have been understood in terms of microstructural models that approximate the material as an array of pores with empirical shape factors used to fit the pore theory to the material. An extension of these theories of acoustics to the thermoacoustic case with an ambient temperature gradient has been proposed by Roh et al. [J. Acoust. Soc. Am. 121, 1413-1422 (2007)] and a model based on Wilsons relaxation approximation for porous acoustics [J. Acoust. Soc. Am. 94, 1136-1145 (1993)] is proposed herein, but the predictions of these analytical models have not been tested successfully against measurements. Accurately characterizing the effects of the applied temperature gradient in a wide bandwidth laboratory setup have proven difficult; as a result, the authors conducted a numerical simulation of propagation within a fibrous geometry in order to test the predictions of the analytical models. The results for several fibrous samples show that the models yield a reliable prediction of thermoacoustic performance from the shape factors and relaxation times.

Video surveillance and counterterrorism: the application of suspicious activity recognition in visual surveillance systems to counterterrorism

Video surveillance systems have become a key element in efforts by security services, the military and law enforcement to counterterrorism since the attacks of 11 September 2001. Primarily involving closed circuit television, collected using a variety of hardware platforms and software algorithms, systematic imagery analysis has typically been used as a tool for post-event forensics to identify tactics, techniques and perpetrators of terrorist attacks. Advanced video surveillance applied to detecting suspicious behaviours embedded in crowd signatures can also be a powerful tool for pre-event deterrence. In this article, we examine case studies of attempts by terrorists to target civilians and create mass casualty incidents and evaluate existing behaviour detection algorithms with the goal of elucidating links between potential threats indicated by suspicious behaviours and possible deterrent mechanisms based on video surveillance.

Hold that line: the New Orleans police strikes

In February 1979, the New Orleans Police Department was engaged in two work stoppages that were orchestrated by the Police Association of New Orleans (PANO). During this period, PANO was affiliated with the International Teamsters Union, which allegedly had ties to organized crime. This study addresses the causes of the police strikes, the right of public safety personnel to strike, and how the “gangster” image of the Teamsters adversely affected the labor negotiations. The authors conducted personal, semistructured interviews of individuals who participated in the labor talks, as well as an extensive review of the literature. According to respondents, the primary causes of the strike were low wages and the refusal of city officials to recognize the police union and enter into meaningful collective bargaining negotiations.

What Is the Role of Behavioral Analysis in a Multilayered Approach to Aviation Security

Since the 1960s, civilian aviation has been a prime target for a myriad of terrorist organizations, which have engaged in asymmetrical tactics such as skyjacking, aircraft bombings, and attacks against airports. The U.S. Transportation Security Administration has employed a multilayered security strategy in an attempt to secure commercial aviation. To that end, behavioral analysis, sometimes referred to as “behavioral profiling,” has become an integral layer of aviation security that monitors the behavior and mannerisms of air travelers. However, the technique is not without critics. The present article examines the current state of behavioral analysis as applied to aviation security and provides recommendations for its proper role and function within a larger security framework.

The forensic analysis of clandestine drug records

Abstract The Racketeering Records Analysis Unit (RRAU) of the Federal Bureau of Investigation (FBI) Laboratory has developed a protocol for the analysis of suspected clandestine and/or coded drug records. Utilizing this procedure, RRAU personnel have been successful in determining (i) whether the records in question are or are not drug records; and (ii) the scope and extent of the illicit drug business as identified in the records.

Dangers from the sea: Considerations of the 1900 Galveston hurricane:

Within the context of homeland security, all organizations must acknowledge the potential of disasters when crafting strategy and pondering contingencies because any number of threats has the potential to disrupt business operations and continuity. Although numerous incidents have affected modern society, the 1900 Galveston hurricane remains the deadliest natural disaster in American history, even surpassing the death tolls of hurricanes Katrina and Sandy. This article examines the Galveston incident from the perspective of communications and the emergency management cycle. Insight is provided regarding the efforts of modern organizations to address possible threats and maintain continuity of operations.

Policies and practices in cold cases: an exploratory study

Purpose – As a result of advances in DNA and other forensic technologies, police agencies are showing increased interest in cold-case investigations, with larger departments dedicating staff to conducting these investigations or forming cold-case squads. The purpose of this paper is to provide information on how police agencies organize and conduct cold-case investigations. Design/methodology/approach – To assess the current practices used in cold-case investigations, an exploratory survey was sent to a stratified random sample of police agencies across the US survey findings are based on 1,051 returns. Findings – Results include the following. Most agencies do little cold-case work, with only 20 percent having a protocol for initiating cold-case investigations, 10 percent having dedicated cold-case investigators, and 7 percent having a formal cold-case unit. Cold-case funding is tenuous: 20 percent of cold-case work is funded through line items in the budget, with most funded by grants or supplemental funds. Success rates for cold-case investigations are low: about one in five cases are cleared. Agency factors associated with higher clearance rates included level of funding and access to investigative databases. Practical implications – As new forensic tools are developed, cold-case investigations will become an increasingly prominent activity of criminal investigation units. The survey reported on in this paper gives the first glimpse of how agencies are handling these cases. Originality/value – To the knowledge, there are no other empirical studies on how agencies structure and conduct cold-case investigations.