Years Of Operational Use Research Articles

LLIN evaluation in Uganda project (LLINEUP): The fabric integrity, chemical content and bioefficacy of long-lasting insecticidal nets treated with and without piperonyl butoxide across two years of operational use in Uganda

Long-lasting insecticidal nets (LLINs) supplemented with the synergist piperonyl butoxide have been developed in response to growing pyrethroid resistance; however, their durability in the field remains poorly described. A pragmatic cluster-randomised trial was embedded into Ugandaʼs 2017–2018 LLIN distribution to compare the durability of LLINs with and without PBO. A total of 104 clusters (health sub-districts) were included with each receiving one of four LLIN products, two with pyrethroid + PBO (Olyset Plus and PermaNet 3.0) and two pyrethroid-only (Olyset Net and PermaNet 2.0). Nets were sampled at baseline, 12 and 25 months post-distribution to assess physical condition, chemical content, and bioefficacy. Physical condition was quantified using proportionate Hole Index and chemical content measured using high-performance liquid chromatography. Bioefficacy was assessed with three-minute World Health Organisation (WHO) Cone and Wireball assays using pyrethroid-resistant Anopheles gambiae, with 1-h knockdown and 24-h mortality recorded. There was no difference in physical durability between LLIN products assessed (P = 0.644). The pyrethroid content of all products remained relatively stable across time-points but PBO content declined by 55% (P < 0.001) and 58% (P < 0.001) for Olyset Plus and PermaNet 3.0 respectively. Both PBO LLINs were highly effective against pyrethroid-resistant mosquitoes when new, knocking down all mosquitoes. However, bioefficacy declined over time with Olyset Plus knocking down 45.72% (95% CI: 22.84–68.62%, P = 0.021) and Permanent 3.0 knocking down 78.57% (95% CI: 63.57–93.58%, P < 0.001) after 25 months. Here we demonstrate that both Olyset Plus and PermaNet 3.0 are as durable as their pyrethroid-only equivalents and had superior bioefficacy against pyrethroid-resistant An. gambiae. However, the superiority of PBO-LLINs decreased with operational use, correlating with a reduction in total PBO content. This decline in bioefficacy after just two years is concerning and there is an urgent need to assess the durability of PBO LLINs in other settings.

Six Years Operational Processing of Satellite data using CATENA at DLR: Experiences and Recommendations

In this article we present the fully automatic processing system CATENA developed at DLR together with experiences and suggestions from six years of operational use. CATENA has been developed since 2007 as a multi-purpose, fully automatic processing system for optical satellite image data. It is used in many projects for operational mass-processing and re-processing of similar satellite data for large coverages or long time-series as requested.

Radar-based alert system to operate a sewerage network: relevance and operational effectiveness after several years of use

Since January 2000, the sewerage network of a very urbanised catchment area in the Greater Nancy Urban Community has been operated according to the alarms generated in real time by a storm alert system using weather radar data. This alert system is based on an automatic identification of intense rain cells in the radar images. This paper presents the characteristics of this alert system and synthesises the main results of two complementary studies realised in 2002 in order to estimate the relevance and the operational effectiveness of the alert system. The first study consisted in an off-line analysis of almost 50,000 intense rain cells detected in four years of historical radar data. The second study was an analysis of the experience feedback after two years of operational use of this alert system. The results of these studies are discussed in function of the initial operational objectives.

Two years of operational use of Subpixel Automatic Navigation of AVHRR scheme: accuracy assessment and validation

Automated techniques for satellite imagery navigation and co-location are especially required for environmental monitoring activities intensively using satellite data. In this work are presented the results obtained after 2 years of operational use of the Subpixel Automatic Navigation of AVHRR (SANA) scheme. An automatic method for accuracy assessment of satellite navigation techniques, which permits a preliminary evaluation of their performances, dealing with a large collection of test images is also proposed. The navigation accuracy assessment, performed by using a selection of small islands as reference points, is discussed. Results achieved over more than 400 Advanced Very-High-Resolution Radiometer (AVHRR) scenes confirm that the SANA scheme is a very accurate one (computed mean navigation error is generally about one AVHRR pixel). Furthermore, because of its high processing speed, it can be considered a suitable tool for intensive satellite data processing in multitemporal analyses, especially required for environmental studies as well as for operational monitoring purposes.

Twenty years of operational use of a risk prediction instrument: The United States parole commission's salient factor score

Although empirically-based recidivism prediction instruments were developed as far back as the 1920s, the adoption of the Salient Factor Score by the federal parole board in 1972—as part of a system of explicit parole decisionmaking guidelines—marked the first time that such an instrument was used in a way that had a definite, measurable impact on paroling decisions. The Salient Factor Score has been used in federal parole decisionmaking continuously for the past twenty years. It is axiomatic that a prediction instrument, particularly an instrument used in actual case decisionmaking, be revalidated periodically to ensure that it has retained predictive accuracy. In this article, the predictive accuracy of the Salient Factor Score over time is examined using data on three, large random samples of federal prisoners released in 1970–1972, 1978, and 1987. In addition, the relationship of the Salient Factor Score to the Criminal History Score of the new federal sentencing guidelines—which apply to defendants convicted of federal offenses committed on or after November 1, 1987—is discussed.

RUDDER ROLL STABILIZATION FOR COAST GUARD CUTTERS AND FRIGATES

ABSTRACTThe potential use of rudders as anti‐roll devices has long been recognized. However, the possible interference of this secondary function of the rudder with its primary role as the steering mechanism has prevented, for many years, the development of practical rudder roll stabilizers. The practical feasibility of rudder roll stabilization has, however, in recent years been demonstrated by two systems designed and developed for operational evaluation aboard two different U.S. Coast Guard Cutters, i.e., Jarvis and Mellon of the 3,000‐ton, 378‐foot HAMILTON Class.The authors describe the major components of the rudder roll stabilization (RRS) system, along with the design goals and methodology as applied to these first two prototypes. In addition, a brief history of the hardware development is provided in order to show some of the lessons learned.The near flawless performance of the prototypes over the past four years of operational use in the North Pacific is documented. Results from various sea trials and reports of the ship operators are cited and discussed.The paper concludes with a discussion of the costs and benefits of roll stabilization achieved using both a modern anti‐roll fin system, as well as two different performance level RRS systems. The benefits of roll stabilization are demonstrated by the relative expansion in the operational envelopes of the USS OLIVER HAZARD PERRY (FFG‐7) Class. The varying levels of roll stabilization suggest that the merits of fins and RRS systems are strongly dependent on mission requirements and the environment.The demonstrated performance of the reliable RRS system offers the naval ship acquisition manager a good economical stabilization system.

Active element in submerged repeaters: first quarter century

The review links the development of British submarine telephony during the last 25 years with the development and production of the active elements, thermionic valves and silicon planar transistors, in the submerged repeater amplifiers. These devices have played a major role in determining the performance, capacity and reliability of all submarine transmission systems. While concentrating on the work of the British Post Office Research Department the complementary role played by industry, and by Standard Telephones and Cables in particular, is recognised. British effort has been encouraged and stimulated throughout by the other major submarine development organisation, Bell Telephone Laboratories in the USA. The development in France of active devices for submarine systems has also been noteworthy. The work on oxide-cathode thermionic valves between 1950 and 1965 is mainly the history of a research and development effort aimed at improving the electrical reliability of the devices. Only in the latter part of the period was any major attempt made to improve valve performance and, consequently, the capacity of submarine systems. The use of systems incorporating valves extends from shallow-water cables around the UK to transatlantic and trans-Pacific cables which have completed a transmission link more than half-way round the world. The target of a 20-year system life, free from failures arising from the decay or collapse in the performance of the valves, has already been achieved for one of the early systems. One of the major links (CANTAT-1, between the UK and Canada) has now passed the 14th year of service satisfactorily. The era of silicon planar transistors, replacing the thermionic valves in submarine systems, started in 1961 and is still continuing. The twin targets of improving performance and reliability were equally stressed during the whole period from 1961 to date. The success in improving device performance is demonstrated by the capacity of the early transistorised systems, 640 (3kHz) circuits, almost double that achieved in the last valve system. Transistor performance has improved still further to provide 1840 circuits in the last transatlantic cable (CANTAT-2, laid in 1974) and later device developments will more than double this figure. The importance of this achievement rests, however, on the maintenance of ultrahigh reliability as an essential feature of performance improvement. An advanced technique for reliability assessment has enabled predictions of less than one active-element failure in a system life of 20 years to be made. It has only been possible to reach this level of reliability by careful design of the transistor and of the processes by which it is made, supplemented by a rigorous system of quality control imposed on materials, piece parts and assembly techniques. Experience of the first eight years of operational use on the sea bed is supporting the reliability predictions. For the future, it is believed that the foundations necessary to support the British effort in this important area of international communications have been well laid. Nevertheless, technical innovation is needed more than ever before to maintain a competitive position in the face of increasing overseas interest in the art of submarine telephony.