Mechanical Seal Failure in the Oil Flooded Compressor

Case StudiesWe consistently experienced mechanical seal failure of the oil–flooded screw compressor in the refrigeration system. The first seal failure happened on July, 2015, which is a year passed since start-up. This seal failure was repeated 4 times every 3 months. All the seal failures were caused by the oil carbonization. These phenomena happened on the outboard seal only and all seal failures’ phenomena were almost same. We finally solved this problem by adjusting the seal face flatnes

Automatic Speech Recognition (ASR) for the Diagnosis of pronunciation of Speech Sound Disorders in Korean children

This study presents a model of automatic speech recognition (ASR) designed to diagnose pronunciation issues in children with speech sound disorders (SSDs) to replace manual transcriptions in clinical procedures. Since ASR models trained for general purposes primarily predict input speech into real words, employing a well-known high-performance ASR model for evaluating pronunciation in children with SSDs is impractical. We fine-tuned the wav2vec 2.0 XLS-R model to recognize speech as pronounced rather than as existing words. The model was fine-tuned with a speech dataset from 137 children with inadequate speech production pronouncing 73 Korean words selected for actual clinical diagnosis. The model's predictions of the pronunciations of the words matched the human annotations with about 90% accuracy. While the model still requires improvement in recognizing unclear pronunciation, this study demonstrates that ASR models can streamline complex pronunciation error diagnostic procedures in clinical fields.Comment: 12 pages, 2 figure

Common Mode Noise Reduction for an LLC Resonant Converter by Using Passive Noise Cancellation

This paper describes the application of a passive noise cancellation method to a prototype inductor-inductor-capacitor (LLC) resonant converter by placing a compensation winding in a transformer to reduce common mode noise. The connection method for the compensation winding is investigated. A circuit analysis is implemented for the displacement currents between the primary and secondary windings in the transformer. The analyzed displacement currents are verified by performing a circuit simulation and a proper compensation winding connection that reduces common mode noise is found. The measurement results show that common mode noise is reduced effectively up to 20 dB in the 1 to 7 MHz frequency region for the prototype LLC resonant converter by using the proposed passive noise cancellation method.clos

Chiral electroluminescence from thin-film perovskite metacavities

Chiral light sources realized in ultracompact device platforms are highly desirable for various applications. Among active media employed for thin-film emission devices, lead-halide perovskites have been extensively studied for photoluminescence due to their exceptional properties. However, up to date, there have been no demonstrations of chiral electroluminescence with a substantial degree of circular polarization (DCP), being critical for the development of practical devices. Here, we propose a new concept of chiral light sources based on a thin-film perovskite metacavity and experimentally demonstrate chiral electroluminescence with DCP approaching 0.38. We design a metacavity created by a metal and a dielectric metasurface supporting photonic eigenstates with close-to-maximum chiral response. Chiral cavity modes facilitate asymmetric electroluminescence of pairs of left and right circularly polarized waves propagating in the opposite oblique directions. The proposed ultracompact light sources are especially advantageous for many applications requiring chiral light beams of both helicities.Comment: 20 pages, 4 figure

Analysis of circularly polarized emission from perovskite thin-film devices

Department of Materials Science and Engineeringclos

Effect of a Monomer Composition on the Mechanical Properties and Glass Transition Temperature of a Waterborne Polyurethane/Graphene Oxide and Waterborne Polyurethane/MWCNT Nanocomposite

Anionic waterborne polyurethane (aWPU) is not compatible with graphene oxide (GO) due to the repulsive force acting on identical ionic charges. In this study, we fabricated cationic surfactant treated GO and cationic surfactant treated carbon nanotube (CNT) to increase the compatibility with aWPU. Cationic waterborne polyurethane (WPU) and nanocomposites thereof were also prepared. On the basis of the mechanical properties of the nanocomposites, glass transition temperature (Tg), and a stability test, it was found that the compatibility between WPU and a nanofiller (NF) was enhanced to a great extent when WPU and NF had opposite ionicity. The Tg and mechanical properties of WPU increased with the addition of NF, showed the maximum value and thereafter decreased with further addition. The effect of composition of ionic monomer in WPU was also investigated. As the composition of the ionic monomer increases, the concentration of NF for the maximum Tg and mechanical properties increases. This was attributed to the ionic association between the NF and WPU

High-frequency analysis and measurement techniques with mixed-mode conversion of induction machine for shaft-voltage prediction

This paper shows high-frequency measurement techniques including phase windings and shaft-ends of a three-phase electrical machine rotating at its rated-rpm, and mixed-mode conversion method for impedance parameters. For the purpose, an external torque source mechanically drives the induction machine, while measuring phase windings and shaft-ends with a vector network analyzer. To investigate common-mode, differential-mode, and inter-phase differential-mode components of drive signals with each shaft-end, we converted the measured impedance parameters to mixed-mode impedance parameters. To verify the converted results, transfer impedances between shaft ends and common-mode component of the mixed-mode parameters are compared with time-domain shaft voltage waveforms that are generated by sinusoidal CM input signals of different frequencies. The comparison showed the mixed-mode impedance parameters match the time-domain waveforms. Also, the mixed-mode parameters showed that common- and differential-mode are more responsible for shaft end-to-end voltage, while common-mode and inter-phase differential-mode are more responsible for shaft-to-frame voltage, for the induction machine. Also, frequency ranges of each mode over which each voltage are more susceptible are specified from the results. ?? 2019 IEEE

Case report: atypical presentation of mpox with massive hematochezia and prolonged viral shedding despite tecovirimat treatment

Abstract Background The outbreak of mpox that occurred between 2022 and 2023 is primarily being transmitted through sexual contact. As of now, there is no consensus on the recommended duration of isolation to prevent sexual transmission of the virus. Moreover, this particular mpox outbreak has presented with distinct complications in comparison to previous occurrences. In this report, we present a case involving severe rectal bleeding from an ulcer in a mpox patient with a history of engaging in receptive sexual contact. Case presentation A 30-year-old Korean man presented at the hospital with complaints of fever, multiple skin lesions, and anal pain. Monkeypox virus polymerase chain reaction (PCR) results were positive for skin lesions on the penis and wrist. The patient received a 12-day course of tecovirimat due to anal symptoms and perianal skin lesions. Following isolation for 12 days and after all skin scabs had naturally fallen off, with no new skin lesions emerging for a consecutive 48 hours—conforming to the criteria of the Korean Disease Control and Prevention Agency—the patient was discharged. However, 1 day after discharge, the patient returned to the hospital due to hematochezia. His hemoglobin level had significantly dropped from 14.0 g/dL to 8.2 g/dL. Sigmoidoscopy unveiled a sizable rectal ulceration with exposed blood vessels, prompting the application of hemostasis through metal clipping. Subsequent monkeypox virus real-time PCR conducted on rectal tissue and swabs yielded positive results (with cycle threshold values of 28.48 and 31.23, respectively). An abdominal CT scan exposed a perirectal abscess, for which ampicillin-sulbactam was administered. Conclusion This case underscores the importance of monitoring for bleeding complications and confirming the resolution of rectal lesions before discharging patients from isolation, particularly in cases where patients have a history of engaging in receptive sexual contact with men or are presenting with anal symptoms