Search Results (10)

Purpose: Pellucid Marginal Degeneration (PMD) is a rare ectatic corneal disorder characterized by inferior peripheral thinning and significant irregular astigmatism. Despite its clinical similarities to keratoconus, PMD presents unique diagnostic and therapeutic challenges. This review aims to provide a comprehensive update on the pathophysiology, clinical features, diagnostic approaches, and management strategies for PMD, emphasizing the latest advancements in treatment options. Methods: A systematic literature search was performed in MEDLINE (via PubMed), Google Scholar, and Scopus up to February 2025 using the terms: “pellucid marginal degeneration,” “PMD,” “ectatic corneal disorders,” “keratoplasty in PMD,” “corneal cross-linking in PMD,” “ICRS in PMD,” “toric IOL PMD” and their Boolean combinations (AND/OR). The search was restricted to English-language studies involving human subjects, including case reports, case series, retrospective studies, clinical trials, and systematic reviews. A total of 76 studies met the inclusion criteria addressing treatment outcomes in PMD. Results: PMD is characterized by a crescent-shaped band of inferior corneal thinning, leading to high irregular astigmatism and reduced visual acuity. Diagnosis relies on advanced imaging techniques such as Scheimpflug-based corneal tomography, which reveals the characteristic “crab-claw” pattern. Conservative management includes rigid gas-permeable (RGP) lenses and scleral lenses, which provide effective visual rehabilitation in mild to moderate cases. Surgical options, such as CXL, ICRS, and toric IOLs, are reserved for advanced cases, with varying degrees of success. Newer techniques such as CAIRS, employing donor tissue instead of synthetic rings, show promising outcomes in corneal remodeling with potentially improved biocompatibility. Penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) remain definitive treatments for severe PMD, though they are associated with significant risks, including graft rejection and postoperative astigmatism. Conclusions: PMD is a complex and progressive corneal disorder that requires a tailored approach to management. Early diagnosis and intervention are critical to optimizing visual outcomes. While conservative measures are effective in mild cases, surgical interventions offer promising results for advanced disease. Further research is needed to refine treatment protocols and improve long-term outcomes for patients with PMD. Full article

Conformity assessment refers to activities undertaken to check whether some product, service or process meets certain criteria and specifications given by internationally accepted standards. The decision on whether a property of interest is aligned with the set standards is made based on measurement. However, uncertainty associated with the measurement results may lead to incorrect decisions. Measurement results may be falsely rejected as non-conforming, although they meet specifications. This is referred to as the producer’s risk. If the measurement result that does not meet the required specifications is accepted as conforming, this is referred to as the consumer’s risk. This paper covers calculations of global consumer's and producer's risk using the Bayesian approach and deals with the application of metrics related to confusion matrices in conformity assessments. These techniques have been used to assess the conformity of the bearing ring diameter with the given specifications. Based on the behavior of these metrics, the optimal length of the guard band was determined with the aim of minimizing the global consumer’s and producer’s risk. Full article

This paper presents a 52-to-57 GHz CMOS quadrature voltage-controlled oscillator (QVCO) with a novel I/Q phase tuning technique based on a body bias control method. The QVCO employs an in-phase injection-coupling (IPIC) network comprising four diode-connected FETs for the quadrature phase generation. The I/Q phase error is calibrated by controlling the body bias voltage offset of the QVCO’s four core FETs. This technique effectively covers a wide range of I/Q phase error between −13.4° and +10.7°. It also minimally induces the unwanted variations in the phase noise, current dissipation, and oscillation frequency, which were found to be only 0.4 dB, 0.07%, and 36 MHz, respectively. After the IPIC-QVCO, a phase-tunable two-stage LO buffer employing a 3-bit switched-capacitor bank was added for additional phase tuning, leading to the extension of the phase tuning range up to −22.7–+20.0°. The proposed QVCO is implemented in a 40 nm RF CMOS process. The measured results show that the QVCO covers a frequency band from 52.4 to 57.6 GHz while consuming 26.2 mW. The phase noise and the figure-of-merit of the QVCO are −91.8 dBc/Hz at 1 MHz offset and −172.4 dBc/Hz, respectively. We also realized a fully integrated 55 GHz quadrature RF transmitter employing the phase-tunable QVCO and LO generator. The effectiveness of the proposed phase-tunable LO generator was confirmed by verifying the image rejection ratio (IRR) calibration at the RF output. Full article

Powerline interference (PLI) is a major disturbing factor in ground-free biopotential acquisition systems. PLI produces both common-mode and differential input voltages. The first is suppressed by a high common-mode rejection ratio of bioamplifiers. However, the differential PLI component evoked by the imbalance of electrode impedances is amplified together with the diagnostic differential biosignal. Therefore, PLI filtering is always demanded and commonly managed by analog or digital band-rejection filters. In electrocardiography (ECG), PLI filters are not ideal, inducing QRS and ST distortions as a transient reaction to steep slopes, or PLI remains when its amplitude varies and PLI frequency deviates from the notch. This study aims to minimize the filter errors in wide deviation ranges of PLI amplitudes and frequencies, introducing a novel biopotential readout circuit with a software PLI demodulator–remodulator concept for synchronous processing of both differential-mode and common-mode signals. A closed-loop digital synchronous filtering (SF) algorithm is designed to subtract a PLI estimation from the differential-mode input in real time. The PLI estimation branch connected to the SF output includes four stages: (i) prefilter and QRS limiter; (ii) quadrature demodulator of the output PLI using a common-mode driven reference; (iii) two servo loops for low-pass filtering and the integration of in-phase and quadrature errors; (iv) quadrature remodulator for synthesis of the estimated PLI using the common-mode signal as a carrier frequency. A simulation study of artificially generated PLI sinusoids with frequency deviations (48–52 Hz, slew rate 0.01–0.1 Hz/s) and amplitude deviations (root mean square (r.m.s.) 50–1000 μV, slew rate 10–200 μV/s) is conducted for the optimization of SF servo loop settings with artificial signals from the CTS-ECG calibration database (10 s, 1 lead) as well as for the SF algorithm test with 40 low-noise recordings from the Physionet PTB Diagnostic ECG database (10 s, 12 leads) and CTS-ECG analytical database (10 s, 8 leads). The statistical study for the PLI frequencies (48–52 Hz, slew rate ≤ 0.1 Hz/s) and amplitudes (≤1000 μV r.m.s., slew rate ≤ 40 μV/s) show that maximal SF errors do not exceed 15 μV for any record and any lead, which satisfies the standard requirements for a peak ringing noise of < 25 μV. The signal-to-noise ratio improvement reaches 57–60 dB. SF is shown to be robust against phase shifts between differential- and common-mode PLI. Although validated for ECG signals, the presented SF algorithm is generalizable to different biopotential acquisition settings via surface electrodes (electroencephalogram, electromyogram, electrooculogram, etc.) and can benefit many diagnostic and therapeutic medical devices. Full article

Radio frequency (RF) filters with multiple passbands can meet the needs of miniaturization and integration for 5G communications. This paper reports a dual-mode Lamb wave resonator (DLWR) and a dual-passband filter based on DLWRs. The DLWR consists of a piezoelectric film and two interdigital electrode (IDT) arrays with different thicknesses, which leads to the coexistence of two main modes in the resonator. The resonance frequencies of the two modes can be adjusted separately by changing the thicknesses of the IDTs, which greatly satisfies the requirements of the dual-passband filter. Four DLWRs with different electrode configurations are designed, and the influences of the periodic length and thicknesses of the IDTs on the performance of the DLWR are studied. When the thickness of the piezoelectric layer is 0.75 μm and the two thicknesses of the IDTs are 0.1 μm and 0.3 μm, the resonance frequency of the second main mode is 1.27 GHz higher than the resonance frequency of the first main mode in the DLWR. Furthermore, a dual-passband filter based on the proposed DLWRs is demonstrated with an insertion loss less than 1 dB and a band rejection of about 15 dB. Moreover, two passbands at 2.45 GHz and 3.88 GHz with bandwidths of 66 MHz and 112 MHz, respectively, are achieved. The presented DLWR shows a potential application that can be used to obtain RF filters with adjustable dual passbands. Full article

The coexistence of TV broadcasting and mobile services causes interference that leads to poor quality-of-service for TV consumers. Solutions usually found in the market involve external band-stop filters along with TV reception log-periodic and Yagi-Uda antennas. This paper presents a log-periodic antenna design without additional filtering that serves as a lower cost alternative to avoid interference from mobile services into the UHF TV. The proposed antenna operates in the UHF TV band (470–790 MHz-passband) and rejects the 800 MHz and 900 MHz bands (stopband) of 4G/LTE-800 and GSM900 services, respectively. Matching to 50 Ohms is very satisfactory in the passband with values of S11 below −12 dB. Furthermore, the antenna is highly directive with a realized gain of approximately 8 dBi and a front-to-back ratio greater than 20 dB. Full article

This work presents a formation method of mechanically-induced long-period fiber gratings using laminated plates. The mechanically-induced long-period fiber grating is temporarily inscribed by compressing the optical fiber between a flat plate and the proposed laminated plate. In turn, the new laminated plate consists of a parallel assembling of single-edged utility blades. We present the experimental characterization of mechanically-induced long-period fiber gratings while employing three laminated plates with a period of 480 ± 20 µm and low duty cycles. These mechanically-induced long-period fiber gratings display a leading rejection band (>15 dB) with a couple of shallow rejection bands (<2 dB) in the range of 1100–1700 nm. This spectral behavior is due to the new mechanical fabrication process that is based on laminated plates that we have proposed, which consists of piling multiple blades with trapezoidal edges that are polished with different levels to obtain different duty-cycles. With the proposed method, we can obtain values of duty-cycles around 10%, much lower than those obtained using traditional methods. Additionally, with this new method, the required mechanical pressure to form the grating is remarkably reduced, which minimizes the probability of the optical fiber failure in the mechanically-induced long-period fiber gratings (MI-LPFGs). Moreover, the proposed mechanically-induced long-period fiber gratings with a single rejection band open the feasibility to implement coarse wavelength division multiplexing systems that are based on long-period fiber gratings. Full article

A new dual-band balanced bandpass filter based on magnetically coupled open-loop resonators in multilayer technology is proposed in this paper. The lower differential passband, centered at the Global Positioning System (GPS) L1 frequency, 1.575 GHz, was created by means of two coupled resonators etched in the middle layer of the structure, while the upper differential passband, centered at a Wi-Fi frequency of 2.4 GHz, was generated by coupling two resonators on the top layer. Magnetic coupling was used to design both passbands, leading to an intrinsic common-mode rejection of 39 dB within the lower passband and 33 dB within the upper passband. Simulation and measurement results are provided to verify the usefulness of the proposed dual-band differential bandpass filter. Full article

Disturbances presented in aeronautical imaging equipment can cause visual axis jitter, which directly leads to a reduction in closed-loop bandwidth and a decrease in tracking accuracy. The disturbance frequency affecting the stable control platform is mainly concentrated in the low- and middle-frequency bands, but the commonly used three closed-loop feedback control methods do not perform well in the disturbance rejection of those frequency bands. Moreover, the only disturbance observer in the acceleration loop cannot improve the low-band disturbance rejection capability due to the drift of the micro-electro-mechanical-system (MEMS) accelerometers in the low-frequency range. To solve these problems, this paper proposed dual disturbance observers (dual DOB) based on the disturbance information in the acceleration loop and the position loop. This design used two compensators to observe and compensate for the disturbances, which did not require additional sensors, and therefore did not increase system cost. Theoretical demonstrations and physical experiments showed that the designed method of the dual DOB not only improved the disturbance rejection capability of the low- and middle-frequency band of the optoelectronic stable control platform, but also improved the robustness of the system. Full article

Radio-frequency interference (RFI) present in microwave radiometry measurements leads to erroneous radiometric results. Sources of RFI include spurious signals and harmonics from lower frequency bands, spread-spectrum signals overlapping the “protected” band of operation, or out-of-band emissions not properly rejected by the pre-detection filters due to its finite rejection. The presence of RFI in the radiometric signal modifies the detected power and therefore the estimated antenna temperature from which the geophysical parameters will be retrieved. In recent years, techniques to detect the presence of RFI in radiometric measurements have been developed. They include time- and/or frequency domain analyses, or time and/or frequency domain statistical analysis of the received signal which, in the absence of RFI, must be a zero-mean Gaussian process. Statistical analyses performed to date include the calculation of the Kurtosis, and the Shapiro-Wilk normality test of the received signal. Nevertheless, statistical analysis of the received signal could be more extensive, as reported in the Statistics literature. The objective of this work is the study of the performance of a number of normality tests encountered in the Statistics literature when applied to the detection of the presence of RFI in the radiometric signal, which is Gaussian by nature. A description of the normality tests and the RFI detection results for different kinds of RFI are presented in view of determining an omnibus test that can deal with the blind spots of the currently used methods. Full article