Decrease In Pitch Research Articles

Numerical investigation of instabilities in over-pressured magnetized relativistic jets

Relativistic jets from active galactic nuclei are observed to be collimated on the parsec scale. When the pressure between the jet and the ambient medium is mismatched, recollimation shocks and rarefaction shocks are formed. Previous numerical simulations have shown that instabilities can destroy the recollimation structure of jets. In this study, we aim to study the instabilities of nonequilibrium over-pressured relativistic jets with helical magnetic fields. Especially, we investigate how the magnetic pitch affects the development of instabilities. We performed 3D relativistic magnetohydrodynamic simulations for different magnetic pitches, as well as a 2D simulation and a relativistic hydrodynamic simulation which served as comparison groups In our simulations, Rayleigh-Taylor instability (RTI) is triggered at the interface between the jet and ambient medium in the recollimation structure of the jet. We find that when the magnetic pitch decreases, the growth of RTI becomes weak but, interestingly, another instability -- the current-driven (CD) kink instability -- is excited. The excitement of CD kink instability after passing the recollimation shocks can match the explanation of the quasi-periodic oscillations observed in BL Lac qualitatively.

2,3-per-acylated α and β cyclodextrins as inducers of helical liquid crystalline phases

ABSTRACT For the first time, a comprehensive study of the mesomorphic, physical and orientation properties of helical mesophases induced by partially acylated cyclodextrins was carried out. Using polarisation microscopy, the formation of a helical mesophase was established when a nematic mixture of polar 4-alkoxy-4’-cyanobiphenyls (CB-2) was doped with chiral 2,3-per-acetylated and 2,3-per-propionylated α- and β-cyclodextrins. The clearance temperatures and helical pitch were measured. The high efficiency of helix twisting under the influence of these dopants and an increase in the orientational order parameter of the liquid crystal matrix were ascertained. Using Haller’s extrapolation method for approximation the temperature dependences of birefringence a decrease in inverse helix pitch (1/p) upon heating was shown to be due to a reduction in the LC order parameter. Quantum chemical simulation of the acetylated α- and β-cyclodextrins structure and their solvates with 4-pentyloxy-4’-cyanobiphenyl was performed, and their interaction energies and dipole moments were calculated. The formation of inclusion compounds of LC molecules into the internal cavity of acylated CDs was established. The higher interaction energy and helical twisting power, as well as the least destabilisation of the mesophase were shown to be observed for β-cyclodextrin derivatives.

Visualization of X-ray fields, overlaps, and over-beaming on surface of the head in spiral computed tomography using computer-aided design-based X-ray beam modeling.

To visualize the X-ray fields, overlaps, and over-beaming on the skin surface during spiral head CT scanning. The measured pitch factors were determined by measuring 3 rotation times, 11 table-feed speeds, and an X-ray beam width. The X-ray fields, overlaps, and over-beaming on the skin surface were calculated via computer-aided design-based X-ray beam modeling, and the values obtained using the nominal pitch and measured pitch factors were compared. The X-ray fields with measured pitch factors exceeded those with nominal pitch factors. The overlaps increased with a decrease in the nominal pitch and measured pitch factors and were observed even at a nominal pitch factor of 1.0. The most stretched over-beaming field was observed with the measured pitch factor of 0.670. The technique can show the overlaps of the X-ray fields and may determine the adequate start angle to prevent overlaps to the eye lens.

Effects of Superthermal Plasmas on Hiss Wave‐Driven Scattering Loss of Radiation Belt Electrons

AbstractPlasmaspheric hiss plays an important role in the loss of radiation belt electrons via cyclotron resonant interactions. The cold plasma approximation is widely used in the evaluation of hiss‐driven electron losses, which however can break down during disturbed periods of geomagnetic storms and substorms. The kappa particle velocity distribution, characterized by a pronounced high‐energy tail, is well‐established to model the profile of superthermal plasma under disturbed geomagnetic conditions. In the present study, by calculating the electron bounce‐averaged pitch angle diffusion coefficients with kappa plasma dispersion relations, we investigate the sensitivity of hiss‐induced cyclotron‐resonant electron scattering loss to the spectral index κ under a variety of superthermal plasma conditions. Our results demonstrate that, with increasing κ, the diffusion coefficients of ∼20–100 keV radiation belt electrons significantly decrease at lower pitch angles and increase at higher pitch angles. In contrast, for electrons at higher energies, the diffusion coefficients tend to increase at lower pitch angles and decrease at relatively higher pitch angles. We also find that decrease of L‐shell and increase of α* and temperature anisotropy tend to weaken the hiss‐driven pitch angle scattering efficiency of electrons at energies from tens to hundreds of keV with a dip at ∼30–50 keV, while the scattering of higher energy electrons can be enhanced. This study confirms the important role of superthermal plasmas in the hiss‐driven electron loss processes and should be carefully incorporated in future modeling of radiation belt electron dynamics.

Effect of spring-wire turbulators with different shapes on heat transfer improvement of solar air heaters; A numerical simulation

This study evaluates the heat transfer and performance characteristics of a solar air heater (SAH) equipped with spring-wire turbulators using a 3D verified CFD simulation process. Five different shapes of spring-wire (as shown in the graphical abstract) are investigated and compared to a flat SAH (without turbulator). The effects of helical diameter, pitch, and wire diameter on the performance of the system are comprehensively analyzed for all five mentioned geometries. The results reveal that the turbulator significantly enhances the thermal efficiency of the SAH within the absorber section. Rectangular cross section shape shows higher enhanced Nu number compared to the other cross section shapes. However, considering both heat transfer and pressure drop, the circular turbulator exhibits the optimal performance. Larger helical diameter, helical pitch and wire diameter, augments, decreases and increases the value of Nu/Nus respectively. Generally, higher increased Nu number also shows higher pumping power as well and that is why thermohydraulic performance parameter (THPP) is considered as well. Larger helical diameter, and helical pitch decreases and increases thermohydraulic performance respectively. For instance, the circular turbulator's THPP rises by approximately 17.5% as the pitch increases from 50 mm to 250 mm. However, the impact of wire diameter on THPP does not show a unified curve trend and depends on the shape of the turbulator. This study is remarkably useful for optimizing the performance of SAHs with turbulators, paving the way for enhanced device efficiency.

Experimental study of a WEC array-floating breakwater hybrid system in multiple-degree-of-freedom motion

Installing an array of wave energy converters (WECs) on an existing breakwater is viable to reduce the high cost and improve the reliability of wave energy applications. The interaction between WECs and floating breakwater under multi-degree-of-freedom motion is crucial but not well investigated, especially the impact of WECs on the mooring system of the breakwater. This article fills this gap by experimentally studying a hybrid system consisting of a rectangle floating breakwater and an array of oscillating body WECs. The interactions between the WEC and the breakwater, the effect of the WEC bottom shape on the hybrid system, and the performance of the hybrid system in waves with different nonlinearities are investigated. Results indicate that the wave amplification effect of the breakwater improves the wave energy conversion performance of the WEC by up to 324.6%. As the WEC absorbs wave energy, the mooring forces of the breakwater in the pitch and surge directions decrease by up to 19.8% and 47.4%, respectively. When the incident wave height increases, the energy extraction performance of the hybrid system improves while the wave attenuation performance decreases. This study provides a reference for the practical application of WEC-breakwater hybrid systems and test data for the validation of numerical methods.

Electroless deposition of nickel microbumps for fine-pith flip-chip bonding

Abstract The reliability of micro-light-emitting diode (Micro-LED) is closely associated with the uniformity of microbumps arrays. With continual decreases in pixel pitch in recent years, it is a challenge to guarantee the uniformity of bump arrays. To satisfy current requirements for ultra-high-density interconnections, this study proposes an electroless plating method for fabricating highly uniform nickel microbumps. This technique differs from electroplating, in which the morphology and consistency of microbumps can be easily controlled. Furthermore, it is a high-selectivity and cost-effective method of microbumps fabrication that eliminates solder wastage and avoids metal lift-off in traditional evaporation. To minimize the non-uniformity of the bumps, we aim to optimize the oxygen plasma treatment parameters and deposition intervals to eliminate the issues of skip plating, hydrogen bubble entrapment, and nodules. Under the combined effect of plasma treatment and intermittent deposition method, microbump arrays with less than 5% uniformity were successfully prepared, achieving the demands of high-density bonding. In addition, the preparation process is highly reproducible, extending the application range of this technique.

Numerical study of the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics

Helical fuel is a promising nuclear fuel proposed to improve the core power density and safety margin. In this study, the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics in helical fuel annuli has been investigated. The volumetric energy source is applied to the fuel pin, and coupled walls are used at the coolant-cladding and cladding-fuel interfaces. The numerical method with SST k-ω turbulence model has been validated with the results of bare annulus. The flow field, fuel central temperature, friction factor, and the circumferential distribution of swirl intensity, heat flux and wall temperature are obtained based on the numerical simulation. The increase in R2/R1 will result in broadening transverse flow region, reducing the gradient of surface heat flux and wall temperature, lowering the maximum wall temperature, but increasing the fuel central temperature and has no significant effect on the friction resistance. The decrease of helical pitch increases the swirl intensity and friction factor, but worsens the heat transfer at the blade roots.

In-depth analysis of pre- and postoperative functional outcome parameters in patients receiving laryngotracheal surgery.

Surgical treatment for airway stenosis necessitates personalized techniques based on the stenosis location and length, leading to favourable surgical outcomes. However, there is limited literature on functional outcomes following laryngotracheal surgery with an adequate number of patients. We conducted a retrospective analysis of patients who underwent laryngotracheal surgery at the Department of Thoracic Surgery, Medical University of Vienna, from January 2017 to June 2021. The study included standardized functional assessments before and after surgery, encompassing spirometry, voice measurements, swallowing evaluation and subjective patient perception. The study comprised 45 patients with an average age of 51.9 ± 15.9 years, of whom 89% were female, with idiopathic being the most common aetiology (67%). Procedures included standard cricotracheal resection in 11%, cricotracheal resection with dorsal mucosal flap in 49%, cricotracheal resection with dorsal mucosal flap and lateral cricoplasty in 24% and single-stage laryngotracheal reconstruction in 16%. There were no in-hospital mortalities or restenosis cases during the mean follow-up period of 20.8 ± 13.2 months. Swallowing function remained intact in all patients. Voice evaluations showed a decrease in fundamental vocal pitch [203 (81-290) Hz vs 150 (73-364) Hz, P < 0.001] and dynamic voice range (23.5 ± 5.8 semitones vs 17.8 ± 6.7 semitones, P < 0.001). However, no differences in voice volume were observed (60.0 ± 4.1 dB vs 60.2 ± 4.8 dB, P = 0.788). The overall predicted voice profile changed from R0B0H0 to R1B0H1. Laryngotracheal surgery proves effective in fully restoring breathing capacity while preserving vocal function. Even in cases of high-grade and complex airway stenosis necessitating laryngotracheal reconstruction, favourable functional outcomes can be achieved.

Structural Origins of the Anisotropic Thermal Expansion of BINOL Crystals

Measurement of the unit cell of (R)-BINOL over a 200° temperature range (300–100 K) reveals an anisotropic contraction where the c-axis contracts ca. 2.3% compared to a ca. 0.45% contraction of the a and b axes, a ca. six-fold difference in linear thermal expansion coefficient. This contraction corresponds to a decrease in the helical pitch of the 31 screw axis in the [001] direction. The anisotropic nature of the contraction is rationalised by a thorough analysis of intermolecular contacts within the crystal and their impact on the conformation of the molecule and crystal packing.Graphical The crystal structure of (R)-BINOL exhibits a pronounced anisotropic thermal expansion.

Fabrication and bonding of In bumps on Micro-LED with 8 μm pixel pitch

Indium (In) is currently used to fabricate metal bumps on micro-light-emitting diode (Micro-LED) chips due to its excellent physical properties. However, as Micro-LED pixel size and pitch decrease, achieving high-quality In bumps on densely packed Micro-LED chips often presents more challenges. This paper describes the process of fabricating In bumps on micro-LEDs using thermal evaporation, highlighting an issue where In tends to grow laterally within the photoresist pattern, ultimately blocking the pattern and resulting in undersized and poorly dense In bumps on the Micro-LED chip. To address this issue, we conducted numerous experiments to study the height variation of In bumps within a range of photoresist aperture sizes (3 μm −7 μm) under two different resist thickness conditions (3.8 μm and 4.8 μm). The results showed that the resist thickness had a certain effect on the height of In bumps on the Micro-LED chip electrodes. Moreover, we found that, with the photoresist pattern size increasing under constant resist thickness conditions, the height and quality of the bumps significantly improved. Based on this finding, we rationalized the adjustment of the photoresist pattern size within a limited emission platform range to compensate for the height difference of In bumps caused by different resist thicknesses between the cathode and anode regions. Consequently, well-shaped and dense In bumps with a maximum height of up to 4.4 μm were fabricated on 8 μm pitch Micro-LED chips. Afterwards, we bonded the Micro-LED chip with indium bumps to the CMOS chip, and we found that we could successfully control the CMOS chip to drive the Micro-LED chip to display specific characters through the Flexible Printed Circuit (FPC). This work is of significant importance for the fabrication of In bumps on Micro-LED chips with pitches below 10 μm and subsequent bonding processes.

Voice and Communication in Transmasculine Individuals One Year Under Testosterone Therapy: A Qualitative Study

Objectives/hypothesesThe purpose of this study was to investigate voice and communication difficulties in transmasculine individuals to develop evidence-based voice and communication training programs. Study designQualitative study. MethodsEight transmasculine individuals, who had received testosterone therapy (TT) for at least 1 year, were included in this study. Semi-structured interviews were conducted by 2 experienced voice clinicians. The software program NVivo was used for transcribing and coding the interviews. Data were processed using a thematic analysis. ResultsThe thematic analysis resulted in the identification of five major themes. Most transmasculine individuals experienced a pitch decrease during the first year of TT and encountered voice-related problems, with a higher incidence during the initial period. Additionally, some participants experienced increased satisfaction with how others attributed their gender after 1 year of TT. However, others still experienced a discrepancy between external gender attribution, self-attribution, and their desired attribution by others. Many participants did not receive voice and communication training. In many cases, voice had a significant impact on their well-being and daily life. ConclusionsIt’s difficult to generalize the results of the current study, since the population of transmasculine individuals is heterogeneous in terms of their subjective gender positioning, desired gender attribution, gender attribution received from others, and gender-related aspects of their vocal situation. Some clients may express dissatisfaction with specific aspects of their voice and communication and may require professional support. Therefore, clinical practice for transmasculine individuals should adopt an individualized approach based on a comprehensive examination of the client's perspective.

Cholesteric Tactoids with Tunable Helical Pitch Assembled by Lysozyme Amyloid Fibrils.

Amyloid fibrils are biological rod-like particles showing liquid-liquid crystalline phase separation into cholesteric phases through a complex behavior of nucleation, growth, and order-order transitions. Yet, controlling the self-assembly of amyloids into liquid crystals, and particularly the resulting helical periodicity, remains challenging. Here, a novel cholesteric system is introduced and characterized based on hen egg white lysozyme (HEWL) amyloid fibrils and the results rationalized via a combination of experiments and theoretical scaling arguments. Specifically, the transition behaviors are elucidated from homogenous nematic, bipolar nematic to cholesteric tactoids following the classic Onsager model and the free energy functional model from Frank-Oseen elasticity theory. Additionally, the critical effects of pH and ionic strength on these order-order-transitions, as well as on the shape and helical pitch of the cholesteric tactoids are demonstrated. It is found that a small increase in pH from 2.0 to 2.8 results in a 34% decrease in pitch, while, on the contrary, increasing ionic strength from 0 to 10mm leads to a 39% increase in pitch. The present study provides an approach to obtain controllable chiral nematic structures from HEWL amyloid fibrils, and may contribute further to the application of protein-based liquid crystals in pitch-sensitive biosensors or biomimetic architectures.

Numerical Comparison of Orifice, Ladder Helical or Segmental Baffle Half-Cylindrical Heat Exchangers

The half-cylindrical heat exchanger is formed by inserting a longitudinal plate in a cylindrical shell space of a U-tube heat exchanger to form dual shell passes for the countercurrent heat transfer purpose. The orifice baffle (OB) in the half-cylindrical shell-side space was proposed to overcome the problems of high-pressure drop in the segmental baffle scheme (SG) and complicated configuration in the unilateral ladder helical baffle scheme (UL). The thermal-hydraulic performances of the bottom part of the half-cylindrical U-tube heat exchanger of four configurations of OBs (fillet triangular, dual-foil square, trefoil, and quatrefoil square), the UL, and the SG were investigated numerically by Fluent in three baffle pitches (50, 40, and 30 mm). The accuracy of the simulated results was validated by experiment with satisfactory agreement. The orifice shape is not sensitive to the performances as long as with a similar flow area. The comprehensive indexes of the schemes OB are very close to that of the UL and much greater than that of the SG, while their overall and shell heat transfer coefficients and pressure drops are lower than those of the schemes UL and SG. Besides, the overall and shell heat transfer coefficients of all schemes increase as the baffle pitch decreases.

Prediction of Voice Outcomes After Hemithyroidectomy Using Skin Electrode Intraoperative Neuromonitoring

Background and Objectives This study focused on predicting voice outcomes following hemithyroidectomy using skin electrode intraoperative neuromonitoring (IONM).Subjects and Method The study involved 82 patients who underwent hemithyroidectomy. During the surgery, the researchers recorded skin IONM values for the vagus nerve and recurrent laryngeal nerve. Voice quality evaluations were conducted before the surgery and at various intervals after the surgery (one week, one month, three months, six months, and one year) using the multidimensional voice program (MDVP), voice handicap index (VHI), and the grade, roughness, breathiness, asthenia, strain (GRBAS) scale. The study aimed to correlate perioperative skin IONM values with subjective and objective voice outcomes.Results The VHI scores increased up to three months post-surgery, with statistically significant changes observed at one week post-surgery. The GRBAS scale scores also increased significantly at one month post-surgery. Similar trends were observed in the MDVP data, including a decrease in the maximum pitch between one week and three months post-surgery. Additionally, the study found that lower delta-V values (difference between the preoperative and postoperative signal amplitude of vagus nerve stimulation) were associated with higher F0 values at one week and three months post-surgery, while jitter and noise-to-harmonic ratio were higher in the group with higher delta-V values at three months post-surgery.Conclusion Greater differences between the preoperative and postoperative signal amplitude of vagus nerve stimulation during surgery were linked to worse postoperative voice outcomes. Voice parameters worsened for up to 3 months after hemithyroidectomy but showed signs of recovery afterwards. These findings offer insights into predicting and managing voice outcomes after hemithyroidectomy.

A Systematic Generalisation of Chord Configuration Methods in Harmonic Writing Based on a Big Data Context

Abstract In this paper, we systematically summarize the chord configuration method in harmonic writing, start from the connection principle of functional harmony, and use the knowledge of harmonic theory to research and explain the harmonic variability writing and chord configuration method. Secondly, based on big data algorithms, it is proposed that according to the chord composition law and progression logic, a chord system construction objective function is proposed, and a dynamic planning algorithm for automatic chord arrangement is designed to realize automatic chord arrangement by machine. Then, after reducing the chord repetition rate of the generated music, it was found that the ideal style type of music could not be achieved. For this problem, a hidden Markov-based chord auto-configuration model is proposed for optimization and experimental analysis of the chord configuration method in harmonic writing is carried out. The results show that the emotional response of the major triad music fragment with an octave decrease in overall pitch is a positive emotion, and the intensity of the emotion is significantly reduced compared to the major triad with no pitch change. The emotional response to the music fragment of the major triad with an octave increase in overall pitch was positive, and the emotional intensity of the major triad with no pitch change was significantly increased. This study improved students’ musical aesthetics, cognitive abilities, and experiences.

Short chiral pitch and blue phase stability in cholesteric liquid crystal mixtures by adding achiral benzoic acid derivative

ABSTRACT Cholesteric liquid crystal (CLC) is anticipated to have applications such as blue light and ultraviolet (UV) light blocking for human skin owing to its selective wavelength reflection against incident sunlight through several hundred nanometres of a periodic helical twist structure. In this study, we investigated short chiral pitch control and enlargement of the blue phase (BP) temperature range by adding an achiral constituent of 4-n-octylbenzoic acid (8 BA) into CLC mixtures composed of three kinds of cholesteryl compounds: cholesteryl chloride, cholesteryl pelargonate and cholesteryl palmitate. Hydrogen bonding dependence of chiral pitch and BP temperature range were also investigated for achiral dopant (8 BA) and CLC mixture through temperature-dependent Fourier-transform infrared analysis. It was found that 40 wt% of 8 BA within the CLC mixture selectively reflected UV and blue light over 360–400 nm with a decrease of chiral pitch. It was also found that the BP temperature range increased by 15.6°C owing to hydrogen bond dimers composed of 8 BA molecules in the CLC mixture.

Conceptual design of narrow annular channel heater with rectangular wire coil for the simulator of solid-fuel thorium molten salt reactor

To heat the simulator core of a solid-fuel thorium molten salt reactor, the narrow annular channel heater with rectangular wire coil separating from the tube wall is proposed. Three-dimensional numerical models are developed, and the simulated result shows that negative axial, radial and tangential velocities in the enhanced narrow annular channel heater are generated compared to the smooth narrow annular channel heater. As the wire width increases and helical pitch decreases, the Nusselt number and friction factor increase. The maximum Nusselt number for enhanced narrow annular channel heater is 5.6 times that for smooth narrow annular channel heater. The overall performance of enhanced narrow annular channel heater is evaluated at a constant pumping power, the value of which is in the range of 1.21–1.85. The best enhanced narrow annular channel heater for the simulator of solid-fuel thorium molten salt reactor is determined based on the overall performance. The maximum outer wall and fluid temperatures of enhanced narrow annular channel heater for the simulator of solid-fuel thorium molten salt reactor are 937.94 K and 931.01 K, which are within the safety limit values of 1143.15 K and 977.15 K, respectively. This design will provide a new method to heat molten salt.

A study on the effect of cell spacing in large-scale air-cooled battery thermal management systems using a novel modeling approach

Recent studies have revealed that effective thermal management systems are necessary to maintain the performance, lifespan, and safety of lithium battery systems. A unique and novel modeling approach is presented in this work with the aim of estimating the thermal performance of air-based cooling systems for large-scale lithium battery packages. The overall model consists of sub-models, including an analytical model for battery cells and a numerical heat and flow model for the battery module, which are validated against experimental data and empirical correlations, respectively. The chosen approach implies that the sub-models can operate independently, allowing accurate transient simulations with reduced processing time. The model is employed to evaluate the effect of cell spacing on the thermal performance of an air-cooled battery system designed for a hybrid electric vehicle. The results demonstrate that the maximum temperature within the cells positively correlates with transverse and longitudinal pitch ratios; however, the maximum temperature difference in the module has a negative correlation with these pitch ratios. In contrast, temperature uniformity shows non-monotonic behavior, making it an applicable criterion to balance between temperature rise and thermal gradients. Moreover, considerable temperature non-uniformity is noted in the early rows, which becomes less significant as pitch ratios decrease.

SHCT: segmented helical computed tomography based on multiple slant source-translation.

Micro-computed tomography (Micro-CT) is inevitably required to inspect long large objects with high resolution. It is well known that helical CT solves the so-called "long object" problem, but it requires that the measured object be strictly located in the lateral field of view (FOV). Therefore, developing a novel scanning method to extend the FOV in both the lateral and axial directions (i.e., the large helical FOV) is necessary. Recently, due to the application of linearly distributed source arrays and the characteristics of easy extension of the FOV and engineering implementation, straight-line scanning systems have attracted much attention. In this paper, we propose a segmented helical computed tomography (SHCT) based on multiple slant source-translation. SHCT can readily extend the helical FOV by adjusting the source slant translation (SST) length, pitch (or elevation of the SST trajectory), and number of scanning circles. In SHCT, each projection view is truncated laterally and axially, but the projection data set within the cylindrical FOV region is complete. To ensure reconstruction efficiency and avoid the lateral truncation, we propose a generalized backprojection-filtration (G-BPF) algorithm for SHCT approximate reconstruction. Experimental results verify the effectiveness of the proposed SHCT methods for imaging large and long objects. As the pitch decreases, the proposed SHCT methods can reconstruct competitive, high-quality volumes.