A ship built from ferromagnetic steel disturbs the uniformity of the Earth’s magnetic field. Changes of ship’s signature are due to the magneto-mechanical interaction of the hull with the Earth’s magnetic field. The ship’s magnetic field can be detected by a magnetic naval mine. For this reason, the vessel has to be demagnetized. There are several methods of ship’s de-perming. The results of experimental and computer simulations of the ship’s de-perming process using coils lying on the seabed are presented in this paper. The simulation of the de-perming process with a hysteresis model of ship’s steel was carried out in Opera-3d 18R2. The laboratory experiments were carried out using a physical ship’s model, several Helmholtz coils, magneto-resistive sensors, etc. The experiments and computer simulations have shown that ship’s de-perming with coils lying on the seabed is possible. The values of coil currents are over dozen times greater than those used in the standard method.
The operating principles of RFID antennas should be considered differently than it is applied in the classical theory of radio communication systems. The procedure of measuring the radiation pattern of antennas that could be applied to RFID transponders operating in the UHF band is seldom discussed correctly in the scientific literature. The problem consists in the variability of the RFID chip impedance that strongly influences measurement results. The authors propose the proper methodology for determining the radiation pattern with respect to an individual transponder as well as an electronically tagged object. The advantage of the solution consists in the possibility of using components of different measuring systems that are available in typical antenna laboratories. The proposed procedure is particularly important in terms of parameter validation - the identification efficiency and costs of an RFID system implementation can be evaluated properly only on the basis of real values of considered parameters.
The operation of an anti-collision RFID system is characterized by the interrogation zone which should be estimated in any direction of 3D space for a group of electronic transponders. The interrogation zone should be as large as possible. However, the many problems in this area are due to the fact that energy can be transferred to transponders only on a limited distance. The greatest flexibility in developing RFID applications and shaping the interrogation zone can be achieved using the system with an antenna multiplexer. Therefore the problem of the interrogation zone determination in HF RFID systems with two orthogonal RWD antennas is presented in the paper. The perceived issues have been effectively dealt with and the solution has been proposed on the basis of the elaborated model. Conducted studies have been used to develop the software tool JankoRFIDmuxHF in the Mathcad environment. The research results are analysed in an example system configuration. The specialized measuring stand has been used for experimental verification of the identification efficiency. The convergence of the measurements and calculations confirms a practical usefulness of the presented concept of interrogation zone determination in anti-collision systems. It also shows the practical utility of the developed model and software tools.
The authors paid particular attention to the problem of antenna impedance measurements in the RFID technique. These measurements have to be realized by using two ports of a vector network analyzer and dedicated passive differential probes. Since the measurement process and estimated parameters depend on the frequency band, operating conditions, type of the system component and antenna designs used, appropriate verification of the impedance parameters on the basis of properly conducted experiments is a crucial stage in the antenna synthesis of transponders and read/write devices. Accordingly, a systematized procedure of impedance measurements is proposed. It can be easily implemented by designers preparing antennas for different kinds of RFID applications. The essence of indirect measurements of the differential impedance parameters is discussed in details. The experimental verification has been made on the basis of a few representative examples.
Temperature change is one of key factors which should be taken into account in logistics during transportation or storage of many types of goods. In this study, a passive UHF RFID-enabled sensor system for elevated temperature (above 58°C) detection has been demonstrated. This system consists of an RFID reader and disposable temperature sensor comprising an UHF antenna, chip and temperature sensitive unit. The UHF antenna was designed and simulated in an IE3D software. The properties of the system were examined depending on the temperature level, type of package which contains the studied objects and the type of antenna substrate.
Background and Aim: Patients with acute pulmonary embolism (APE) associated with hemodynamic instability, i.e. high-risk APE (HR-APE), are at risk for early mortality and require urgent reperfusion therapy with thrombolysis or embolectomy. However, a considerable proportion of HR-APE subjects is not reperfused but only anticoagulated due to high bleeding risk. The aim of the present study was to assess the management of HR-APE in a single large-volume referral center. Methods: A single-center retrospective study of 32 HR-APE subjects identified among 823 consecutive patients hospitalized for symptomatic APE. Results: Out of 32 subjects with HR-APE (19 women, age 69 ± 19 years), 20 patients were unstable at admission and 12 subsequently deteriorated despite on-going anticoagulation. Thrombolysis was applied in 20 (62.5%) of HR-APE subjects, limited mainly by classical contraindications in the remainder. Percutaneous pulmonary embolectomy was performed in 4 patients. In-hospital PE-related mortality tended to be higher, albeit insignifi cantly, in the patients who developed hemodynamic collapse during the hospital course compared to those unstable at admission (67% vs. 40%, p = 0.14). Also, survival was slightly better in 22 patients treated with thrombolysis or percutaneous embolectomy in comparison to 10 subjects who received only anticoagulation (54% vs. 40%, p = 0.2). Major non-fatal bleedings occurred in 7 of 20 patients receiving thrombolysis (35%) and in 2 (17%) of the remaining non-thrombolysed 12 HR-APE subjects. Conclusions: Hemodynamically instability, corresponding to the definition of HR-APE, affects about 4% of patients with APE, developing during the hospital course in approximately one-third of HR-APE subjects. As almost 40% of patients with HR-APE do not receive thrombolytic therapy for fear of bleeding, urgent percutaneous catheter-assisted embolectomy may increase the percentage of patients with HR-APE undergoing reperfusion therapy. Further studies are warranted for a proper identification of initially stable intermediate-risk APE subjects at risk of hemodynamic collapse despite appropriate anticoagulation.