Linearized 9-Bit Hybrid LBDD PWM Modulator for Digital Class-BD Amplifier

The paper presents an original architecture andimplementation of 9-bit Linearized Pulse Width Modulator(LPWM) for Class-BD amplifier, based on the hybrid methodusing STM32 microcontroller and Programmable Tapped DelayLine (PTDL). The analog input signals are converted into 12-bitPCM signals, then are directly transformed into 32-bit LBDDDPWM data of the pulse-edge locations within n-th period of theswitching frequency, next requantized to the 9-bit digitaloutputs, and finally converted into the two physical trains of 1-bitPWM signals, to control the output stage of the Class-BD audioamplifier. The hybrid 9-bit quantizer converts 6 MSB bits usingcounter method, based on the peripherals of STM32microcontroller, while the remaining 3 LSB bits - using a methodbased on the PTDL. In the paper extensive verification ofalgorithm and circuit operation as well as simulation inMATLAB and experimental results of the proposed 9-bit hybridLBDD DPWM circuit have been performed. It allows to attainSNR of 80 dB and THD about 0,3% within the audio baseband

Early fetal cardiac scan as an element of the sonographic first-trimester screening

Early fetal cardiac scan (EFCS) is becoming an increasingly common element of the first trimester ultrasound screening carried out at 11-14 gestational weeks. It offers the first possibility to detect congenital heart defects (CHD) or, in ambiguous cases, to identify those pregnancies where a more detailed cardiac scan would be required later in pregnancy. The size of the fetal heart at the end of the first trimester and the associated relatively low image resolution make it impossible to capture all cardiac data to inform the ultimate picture. However, even at this stage, cues of anatomical and functional abnormalities can be picked up, which suggest not only a CHD, but also a likelihood of cardiovascular symptoms typical of genetic disorders. EFCS should focus on cardiac position, atrioventricular (AV) connections, AV valve function, initial assessment of ventriculo-arterial (VA) connections and the presence of red flag signs in the three vessel and trachea view (3VTV). Proper use of color Doppler mapping makes it possible to overcome the low resolution of B-mode to a certain extent. Here we present our long-term experience in EFCS

Testing the wear of wheelsets of EN97 series vehicles in terms of geometrical parameters of the wheel profile in two-year operation

The article presents the results of wheel wear tests of selected EN97 series electric multiple units. In the tests carried out on the 14 vehicles mentioned above, which were driven on the same route, geometrical parameters of the profile of all wheels were recorded during periodic inspections. The analyzed data concerned the period of over two years of use, when the vehicles were delivered from the manufacturer to the carrier as new. In the form of graphs, cases of exceeding a given parameter in relation to the requirements set in the Maintenance System Documentation are presented, broken down into individual wheelsets. The article presents the results of operational tests, which show which wheel set parameters (wheel diameter, rim steepness, rim thickness, rim height, etc.) are most often exceeded and which are least. The analyzes of the geometric parameters of the wheel profile on the tested group of vehicles, which were used on the same route in the same period, clearly prove that the parameters most often exceeded are wheel diameter and rim steepness. These two exceeded parameters were the basis for turning the wheelsets

Evaluation of weight wear of disc brake pads after test stands

The article presents the results of the research of a railway disc brake in the evaluation of the weight wear of friction pads. The tests were carried out on a certified brake stand where the friction and mechanical characteristics of the brake are determined. The stand was additionally equipped with a thermal imaging camera to observe the contact of the pads with the brake disc. Attention was also paid to examining the influence of such parameters of the braking process as the contact surface of the pad with the disc, the thickness of the pads as a determinant of their initial wear, the pressure of the pads to the disc, braking mass and braking speed on the weight wear of the friction pads

Obrzęk limfatyczny kończyny górnej po radykalnym leczeniu chorych na raka piersi – aktualne zasady postępowania

Upper limb lymphedema (ULL) is the most severe late complication following radical treatment of breast cancer (BC). It can be caused by both cancer recurrence and previous therapy (lymphadenectomy, axillary radiotherapy). In BC survivors, ULL- inducing factors include: previous irradiation treatment, infections within the upper limb or the scar, high BMI. Diagnosis of ULL makes use of measurements of the circumference and volume of the limb, imaging, measuring electrical impedance of tissues and lymphoscintigraphy which determines the type and severity of lymph flow disturbances. ULL has a chronic and progressive nature leading to physical, psychic and social disability and, on rare occasions, to secondary neoplasms of the lymphatic system. Therapeutic management involves: patients’ education, complex physical therapy (manual lymphatic drainage, compression therapy), reduction and drainage surgery (microsurgery) as well as liposuction. The most effective conservative procedures include complex physical therapy and particularly manual lymphatic drainage with compression therapy. Failure of conservative therapy indicates the need for surgery. Liposuction is a currently preferred surgical procedure because of its simplicity and a low percentage of complications. Surgery should be complemented by constant compression therapy. Due to low efficiency of all the methods applied, ULL prevention is of paramount importance. It should consist in rationalising indications for oncological treatment (lymphadenectomy, radiation therapy)

New approach to brake pad wear modelling based on test stand friction-mechanical investigations

The paper presents the results of investigations of a railway disc brake system related to the mass wear of its brake pads. The tests were carried out on a certified brake stand designed to determine the friction-mechanical characteristics of the brakes. The test stand was additionally equipped with a thermographic camera to observe the contact points of the brake pads with the disc. Particular attention was drawn to investigating the impact on the mass wear of the brake pads of such parameters of the braking process as contact surface of the brake pad with the rotor, thickness of the brake pads as the indicator of their initial wear, clamping force of the pads against the rotor, rail vehicle mass to be decelerated, and speed, at which the deceleration begins. The scientific aim of the paper is to present the relations between the mass wear of the brake pads and the quantities that characterize the braking process. A regression model was determined to estimate the wear of the brake pads based on a single braking process with the preset input quantities

Generation of a Multicomponent Library of Disulfide Donor-Acceptor Architectures Using Dynamic Combinatorial Chemistry

We describe here the generation of new donor-acceptor disulfide architectures obtained in aqueous solution at physiological pH. The application of a dynamic combinatorial chemistry approach allowed us to generate a large number of new disulfide macrocyclic architectures together with a new type of [2]catenanes consisting of four distinct components. Up to fifteen types of structurally-distinct dynamic architectures have been generated through one-pot disulfide exchange reactions between four thiol-functionalized aqueous components. The distribution of disulfide products formed was found to be strongly dependent on the structural features of the thiol components employed. This work not only constitutes a success in the synthesis of topologically- and morphologically-complex targets, but it may also open new horizons for the use of this methodology in the construction of molecular machines