Shallow Recess Research Articles

Effects of Recess Depth and Orifice Diameter on Pneumatic Hammer Instability in Hydrostatic Thrust Bearings: Analysis and Experimental Validation

Abstract Hydrostatic thrust bearings (HTBs) are required in various turbomachinery systems due to their substantial load capacity and superior rotor axial positioning capabilities, which minimize friction and heat generation. However, when lubricated with compressible fluids, these bearings can experience pneumatic hammer instability especially if the recess volume is significant. This study aims to establish design guidelines and experimentally validate the performance of hydrostatic thrust bearings, with a focus on predicting and mitigating pneumatic hammer instability. The research includes an investigation into the static load characteristics of these bearings when operated with air as the lubricant. The analysis in this paper covers the effects of varying supply pressures, recess depths, and orifice diameters on pneumatic hammer instability, as well as on the load capacity, stiffness, and damping coefficients of the bearings. To validate these findings, experiments are conducted using two test bearings with differing recess depths and orifice diameters. The results from both predictive models and experimental data consistently show that a shallow recess depth is effective in preventing pneumatic hammer instability without notably diminishing the bearing load capacity. Nonetheless, modifying the orifice diameter to control pneumatic hammer instability requires careful design consideration, as it might lead to decreased load capacity and stiffness. This research addresses the challenge of preventing pneumatic hammer instability in hydrostatic thrust bearings through a combined approach of numerical analysis and experimental testing. It contributes significantly to the field by offering practical design recommendations for optimizing recess depth and orifice diameter. These guidelines aim to eliminate pneumatic hammer instability while preserving critical performance aspects of hydrostatic thrust bearings, such as load capacity and stiffness.

A circular hydrostatic shallow recess thrust bearing integrating a micro-range tilting axis

This article investigates the integration of a micro-range (± 10 µrad) tilting axis into a shallow recess hydrostatic thrust bearing. The working principle relies on pressure taps machined into the bearing geometry, enabling the external manipulation of the local pressure distribution, causing a change in film geometry to restore equilibrium. To estimate the possibilities and limitations, the article presents a theoretical approach to calculate the properties of the integrated tilting axis and the influence on the inherent tilting stiffness of the bearing. Furthermore, performed measurements at 10 µm film height and 10 MPa supply pressure validate the proposed theory. This technology enables the extension of a conventional hydrostatic bearing by a robust, highly sensitive, and low-cost micro-range tilting axis.

The interaction mechanism between zein and folic acid in alkaline aqueous solutions: an experimental and molecular simulation study

Abstract Objectives Folic acid is a vitamin that is not highly soluble in water and is sensitive to the environment. Therefore, it is important to find suitable carriers. This study aimed to exemplify the interaction of folic acid with zein in alkaline aqueous solutions and shed light on how zein can be used as a carrier for folic acid. Materials and Methods Zein and folic acid were separately dissolved in NaOH solutions with a PH of 11.5. Zein solution and folic acid solution were combined in specific ratios. Various methods including multi-spectroscopy, dynamic light scattering, and electron microscopy combining with molecular dynamics simulations were used to study the interaction mechanism between zein and folic acid in alkaline aqueous solutions. Results Fluorescence spectroscopy showed that the quenching of zein by folic acid was mainly static, and the main driving force behind this interaction was van der Waals forces and hydrogen bonds. The formation of zein–folic acid complexes was confirmed by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy. The results also showed that the structure of zein changed when it interacted with folic acid. Dynamic light scattering analysis revealed that the addition of folic acid caused proteins to aggregate. The aggregates of the complexes had an irregular shape and were large, as observed by scanning electron microscopy and transmission electron microscopy. Molecular simulation was used to further investigate the interaction mechanisms. According to these findings, the folic acid molecule interacted with zein in a shallow recess near the protein surface. The dominant forces at play in the zein–folic acid interaction were van der Waals forces and electrostatic forces, including hydrogen bonding. Conclusion The zein alkali-soluble system is very suitable for folic acid delivery.

Experimental and theoretical study on the dynamic stiffness of circular oil hydrostatic shallow recess thrust bearings

The dynamic stiffness of traditional (deep recess) hydrostatic bearings decreases due to the fluid compressibility between the bearing and a compensation device, e.g., a capillary. Shallow recess bearings, on the other hand, reduce the influence of fluid compressibility on dynamic stiffness through a reduced compressible volume and inherent stiffness. This article outlines a theoretical and experimental study of the dynamic stiffness of oil hydrostatic shallow recess thrust bearings without external compensation devices and in combination with external capillaries. The measurements performed in the study validate the theoretical models and the potential to increase dynamic stiffness. In addition, analytical solutions are proposed for the stiffness and damping of a circular shallow recess thrust bearing.

Analytical derivation and experimental verification of principle of a 3 DOF sensor integrated in an oil hydrostatic shallow recess thrust bearing

This article presents a sensing thrust bearing based on pressure sensors, utilizing the pressure profile sensitivity to a change in film geometry. The pressure is measured locally via pressure taps, machined into the bearing geometry. To evaluate the pressure signals, the sensitivities are derived analytically for both axial and angular displacement. Further, an experimental study was performed at 10 µm film height and 10 MPa supply pressure, which shows a strong agreement with the presented theory and demonstrates the possibility to measure, relative to the film height, large as well as small displacements with a repeatability in the order of sub-µm and sub-µrad.

EXPERIMENTAL STUDY ON TILTING STIFFNESS OF OIL HYDROSTATIC SHALLOW RECESS THRUST BEARINGS

Circular shallow recess bearings generate a not rotationally symmetrical pressure profile if they are not aligned parallel. The throttling effect of the shallow recess makes this response possible. Furthermore, the generated pressure profile acts against the tilting. As a result, a shallow recess bearing generates a tilting stiffness. This article outlines an experimental approach to characterize the tilting stiffness of an oil hydrostatic shallow recess thrust bearing with micro step and gap height. For this purpose, we developed a small test bench. The measured tilting stiffnesses are compared with a numerical solution based on the 2D-Reynolds equation.

A case of gastric and duodenal mucosa-associated lymphoid tissue lymphoma with multiple gastric cancers: a case report

BackgroundGastric mucosa-associated lymphoid tissue (MALT) lymphoma is often caused by Helicobacter pylori and has a good prognosis. Rarely, patients with MALT lymphoma may have gastric cancer and have a poor prognosis.Case presentationWe herein report a case in which surgical treatment was achieved for a 72-year-old male patient with gastric and duodenal MALT lymphoma coexisting multiple gastric cancers. He underwent upper endoscopy for epigastric discomfort, which revealed mucosal erosion on the posterior wall of the middle body of the stomach, an elevated lesion on the duodenal bulb, and a raised tumor on the antrum of the stomach. He was diagnosed with gastric and duodenal MALT lymphoma with early gastric cancer. One month after H. pylori eradication, a second upper endoscopy revealed no improvement in the gastric or duodenal mucosa, and areas of strong redness with a shallow recess just below the cardia of the stomach. As a result, a diagnosis of gastric and duodenal MALT lymphoma with two gastric cancers was made. Total gastrectomy with proximal duodenum resection using intraoperative upper endoscopy and regional lymph node dissection was performed. Pathologically, gastric and duodenal MALT lymphoma and three gastric cancers were detected. Since one of them was an advanced cancer, he started taking S-1 after his general condition improved.ConclusionFor early detection of gastric and duodenal MALT lymphoma or gastric cancer, appropriate upper endoscopy and a biopsy are important. It is necessary to select a suitable treatment, such as H. pylori eradication, endoscopic treatment, surgery, chemotherapy, and irradiation, according to the disease state.

Numerical study of the effect of surface grooves on the aerodynamic performance of a NACA 4415 airfoil for small wind turbines

Indented surface grooves can eliminate the laminar separation bubbles formed on airfoil surfaces, and thus have the potential to improve the aerodynamic performance of small wind turbines. In this study, a three-equation transitional turbulence model was selected and validated with experimental data to simulate the 2D flow around a NACA 4415 airfoil. Parametric simulation of surface groove characteristics was then conducted to investigate their effects on aerodynamic behavior. It was found that the recess depth ratio (h/δ, h: groove recess depth, δ: baseline boundary layer thickness) is the key influencing factor among the groove feature parameters, with the most effective value between h/δ=1.0 and 1.5. A smaller aspect ratio of recess depth to groove width is required to trap the vortex for a shallow recess depth, while a higher aspect ratio can stabilize the vortex for a deep recess. The endpoint of a groove can affect the potential vortex size within it, and the optimum endpoint is located around 0.16c (c: airfoil chord). Moreover, a rectangular groove especially for a recess depth ratio h/δ=1.2−1.5 offers better aerodynamic performance than an arc groove, as the rectangular configuration more efficiently restricts the flow motion inside the groove.

The Impact of Gate Recess on the H₂ Detection Properties of Pt-AlGaN/GaN HEMT Sensors

The present work reports on the hydrogen gas detection properties of Pt-AlGaN/GaN high electron mobility transistor (HEMT) sensors with recessed gate structure. Devices with gate recess depths from 5 to 15 nm were fabricated using a precision cyclic etching method, examined with AFM, STEM and EDS, and tested towards H2 response at high temperature. With increasing recess depth, the threshold voltage ( ${V}_{\textit {TH}}$ ) shifted from −1.57 to 1.49 V. A shallow recess (5 nm) resulted in a 1.03 mA increase in signal variation ( $\Delta {I}_{\textit {DS}}$ ), while a deep recess (15 nm) resulted in the highest sensing response ( ${S}$ ) of 145.8% towards 300 ppm H2 as compared to reference sensors without gate recess. Transient measurements demonstrated reversible H2 response for all tested devices. The response and recovery time towards 250 ppm gradually decreased from 7.3 to 2.5 min and from 29.2 to 8.85 min going from 0 nm to 15 nm recess depth. The power consumption of the sensors reduced with increasing recess depth from 146.6 to 2.95 mW.

The fibre shear supplement of precast beam-half joints using steel fibre self-compacting concrete

The end region of the dapped-end beam experienced multiaxial stress actions, which requires high amounts of reinforcement and this resulted to the closely space reinforcement. Therefore, hooked-end steel fibres were mixed into all beam specimens to partly replace the secondary shear and bursting reinforcement to reduce the congestion issue. A series of experiments were performed on shallow recess (SR) and deep recess (DR) half joint beams to examine the partial reduction of reinforcement with 1% replacement of steel fibre. All SR and DR beams were then tested under shear load to study the effectiveness of steel fibres over traditional reinforcement in resisting loads, with two different shear span-to-depth ratios, which are 1.4 and 2.1. The experimental shear strength fibre supplement results for the SR and DR beam specimens were compared with theoretical predictions using the analytical and RILEM methods. The incorporation of 1% of steel fibre in the concrete matrix has the ability to replace 50% of horizontal and vertical reinforcement in SR and DR beams. In general, it is found that both the analytical and RILEM methods give a close approximation for the experimental DR beam specimen values, but slightly overestimated the fibre shear supplement of SR beam specimens by 13.4%. The results support the ability of steel fibres to resist tensile stress through its fibre-bridging action.

650-V Double-Channel Lateral Schottky Barrier Diode With Dual-Recess Gated Anode

An AlGaN/GaN double-channel Schottky barrier diode (DC-SBD) with dual-recess gated anode is demonstrated in this letter. The DC-SBD features two recess steps. The deep one cuts through two channels, and the anode metal contacts 2DEG directly from the sidewall of the recessed heterostructure. The shallow one terminates at the upper channel layer and is located adjacent to the Schottky contact. A MOS field plate is placed on the shallow recess region to pinchoff the underlying channels, so the off-state leakage current of the DC-SBD can be suppressed. Since the lower channel is separated from the etched surface, the field-effect mobility beneath this MOS structure shows a high peak value of 1707 cm2/( $\text {V}\cdot \text {s}$ ). The DC-SBD with an anode-to-cathode length ( ${L}_{\text {ac}}$ ) of $15~\mu \text{m}$ exhibits a turn-on voltage ( ${V}_{\text {T}}$ ) of ~0.6 V (at 1 mA/mm), a leakage current of 7.8 nA/mm (at −100 V), and a breakdown voltage of 704 V (at $1~\mu \text{A}$ /mm). The double-channel design also allows both the deep and shallow recesses to be terminated at GaN layers that results in high uniformity of ${V}_{\text {T}}$ .

DC and RF Characteristics of Enhancement-Mode Al2O3/AlGaN/GaN MIS-HEMTs Fabricated by Shallow Recess Combined with Fluorine-Treatment and Deep Recess

Enhancement-mode (E-mode) Al2O3/AlGaN/GaN MISHEMTs were fabricated by shallow recess combined with CF4 plasma treatment (SR/F) and deep recess (DR) to compare the effect of each process technique on the device performance. To prevent the device performance degradation induced by plasma damage during gate recess, the digital etch technique was employed. The fabricated E-mode devices have positively shifted threshold voltage, and exhibit lower transconductance (gm) and saturation drain current than depletion-mode devices. Due to the CF4 plasma damage during F-treatment, SR/F shows a sharp drop of gm curve and low saturation drain current. In contrast, DR presents broad gm and high saturation drain current. It is also revealed that the digital etch for gate recess exhibits an isotropic etch profile, consequently increasing the on-resistance. There is no remarkable difference between SR/F and DR in fT and fmax, but DR has a better linearity over SR/F owing to the absence of plasma damage during F-treatment. This results reveal that the DR using digital etch is promising technique to obtain the high performance E-mode MISHEMTs compared to the F-treatment.

Analytical Research on Characteristics of Deep-shallow Journal Bearings with Orifice Restrictors

Hydrodynamic-static hybrid journal bearing with orifice restrictor is a kind of bearing that the throttling effect is realized by orifice restrictor and the second throttling effect is realized by shallow recess. There is a shortage of the existing theory that can not study the load characteristics which are affected by the recess structure parameters and operation parameters in analytical method. It is inconvenient for engineers to use the computational fluid dynamics software, due to the disadvantage of long period of calculation. On the assumption of subsection linearization of pocket pressure, a method is proposed to analyze the deep-shallow bearing characteristics, such as load capacity, bearing stiffness, flow rate and temperature ascending relationship. The analytical method is used to study bearing characteristics with the different structure parameters and working parameters, such as supply pressure, spindle speed, oil inlet aperture, shallow depth and initial oil film thickness. It is demonstrated that stiffness is close to the biggest value and temperature rising is close to the lowest one, when the shallow depth is thicker than the initial oil film by twice or three times, in the conditions that all other structural parameters and operating parameters are unchanged. The reliability of the analytical method has been verified by comparing experimental results with the analytical values.

Surgical implantation of the Sophono transcutaneous bone conduction system

Bone conduction implantable devices are an effective means of rehabilitation for ipsilateral conductive hearing loss and in a contralateral routing of signal (CROS) configuration for single-sided deafness. Percutaneous systems provide excellent sound quality but suffer from the complications of recurrent infection, skin overgrowth, and cosmetic concerns. The Sophono transcutaneous bone conduction system uses an internal retention magnet to hold an external force plate and sound processor to the scalp, allowing for transcutaneous bone conduction and stimulation of the cochlea. Implantation consists of a simple incision, drilling a shallow recess for the bilobed magnet in the cranium, and securing of the implant with standard plating screws. Surgical considerations such as placement, flush positioning to the bone, and maintaining or augmenting overlying tissue thickness are important to ensuring postactivation wearability. Fitting considerations such as time to fitting, magnet strength determination, and graduated wearing schedules are also critical to patient outcomes.

Performance Analysis of High-Speed Deep/Shallow Recessed Hybrid Bearing

The present paper proposes a theoretical analysis of the performance of deep/shallow recessed hybrid bearing. It is intended that, on the basis of the numerical results drawn from this study, appropriate shallow recess depth and width can be determined for use in the bearing design process. By adopting bulk flow theory, the turbulent Reynolds equation and energy equation are modified and solved numerically including concentrated inertia effects at the recess edge with different depth and width of shallow recess. The results indicate that the load capacity, drag torque increases as the depth of shallow recess is shallower and the width ratio (half angle of deep recess versus half angle of shallow recess) is smaller. In contrast, the flow rate decreases as the depth of shallow recess is shallower and the width ratio is smaller. Nevertheless, the appropriate design of the depth and width of shallow recess might well induce the performance of high-speed deep/shallow recessed hybrid bearing.

50 Years Ago in CORR: Acrylic Hip Endoprostheses Dana M. Street MD CORR 1955;6:72-85

The replacement of diseased and injured joints has developed into one of the most successful surgical procedures ever developed to durably relieve pain and restore function. According to Street [10], “The desire to replace a diseased or a worn-out joint by a mechanically perfect indestructible artificial one always has been present on the part of both doctor and patient.” However, it took well over half a century from the first attempts to achieve the goal of reliable pain relief and restoration of function. The first attempts were arguably by Gluck in 1891 [3] and independently by Pean in 1894 [7, 9] and 1897 [8]. Gluck attempted to replace the ankle, knee, wrist, and hip, and experimented with bone cements, but all his operations failed from infection [2]. Pean devised several types of shoulder arthroplasties, including one replacing both sides of the joint. Until Charnley introduced the modern artificial hip dependent upon cementing the device in bone in 1961 [1], most attempts at best modestly achieved the goals. In the early 1950 s, Moore [6] and the Judet brothers [4] introduced the first prostheses that achieved widespread use, both in hips. These two implants were of distinct designs in that the former was all metal with an uncemented femoral stem while the latter was acrylic with a short stem extending only into the femoral neck. Both replaced only the femoral head. Street introduced an acrylic and metal prosthesis of his own design in 1955. “When the work of Judet first appeared in the literature, we adopted a policy of waiting to see what the long-term results would be and resisted the temptation successfully for about 2 years to try this method” [10]. Since he had ready availability of a machine shop, he varied the design according to the condition, and some of his implants had short stems (“Types I and 2,” Figs. 1 and ​and2)2) while others had long stems (“Type 3,” Fig. 3). By 1955, he had operated on 50 patients with these various devices and with a minimum followup of 4 months. The Type 3 was the most durable in this short term study (Table 2) and these patients were clearly improved compared to their preoperative condition. Street commented, “The ideal prosthesis (1) causes no tissue reaction, (2) restores the normal mechanics, (3) is stable, (4) conserves maximum of normal bone or ligamentous tissue and (5) will not, a, break or, b. wear” [10]. Fig. 1 Type 1 prosthesis: acrylic head with shallow recess, hub at base of steel trifin nail. (Reprinted with permission and © Lippincott Williams & Wilkins, from Street DM. Acrylic hip endoprostheses. Clin Orthop Relat Res. 1955;6:72–85.) ... Fig. 2 Type 2: similar head to Type 1, 3 small supplementary trifin nails placed to come within cortex of neck; nails are Vitallium. (Reprinted with permission and © Lippincott Williams & Wilkins, from Street DM. Acrylic hip endoprostheses. Clin ... Fig. 3 Type 3: acrylic head and neck, taper without abutment to allow settling to stable position; steel diamond-shaped nail. (Reprinted with permission and © Lippincott Williams & Wilkins, from Street DM. Acrylic hip endoprostheses. Clin Orthop ... Table 2. Results Street’s perspective reflects his time. If the concept and importance of long term followup had been emphasized by Codman in the early part of the 20th century [5], it had not become widespread and clearly, Street’s implied concept of long term would have been considerably shorter than the 10–20 years or more we consider today as standard for joint arthroplasty. Although Street’s criteria for an ideal prosthesis would be included among today’s criteria, Street mentioned no criteria related to the patient. For the patient the important criteria are that a joint implant procedure reliably and durably relieve pain and restore function with a low risk of complications. In these days of “evidence-based medicine” we place emphasis on patient-centered outcome measurements. Street’s article and device let us know how far we have advanced. It is through the efforts of these pioneers we have made progress.

Successful Endoscopic Management of Fish Bone Embedded into the Bladder Wall

We report a case of a pyogenous vesical abscess resulting from an ingested fish bone embedded in the bladder wall that was treated endoscopically in an asymptomatic man. Computed tomography of the abdomen showed a linear radiopaque structure in the thickened left anterolateral wall of the bladder. Cystoscopy revealed a protruding mass, covered with normal-appearing mucosa, with outflow of pus from a shallow recess. Histopathological findings indicated that the transurethrally removed linear structure, located in the submucosa, was compatible with fish bone. A high index of suspicion should be maintained for the correct diagnosis to be made.

Numerical Study of the Pressure Pattern in a Two-Dimensional Hybrid Journal Bearing Recess, Laminar, and Turbulent Flow Results

The present work is a parametric study of the pressure pattern in a two-dimensional recess of a hybrid journal bearing (HJB). It is known that theoretical models of HJB are largely dependent on the recess pressure pattern especially for severe working conditions (high rotation speeds, shallow pockets, etc.). The difficulty is that the recess flow is dominated by the interaction of viscous and inertia forces and cannot be analyzed using a thin film model. The present analysis is based on the numerical resolution of the two-dimensional Navier-Stokes equations where only one recess is modeled (with the film lands and the supply region), the fluid being regarded as incompressible and isothermal. Both the laminar and the turbulent flow regimes are considered. The study is governed by two parameters, one related to the HJB operating conditions and the other related to the recess geometric characteristics. The first parameter is the ratio of the runner versus the supply Reynolds number, Rer/Res∈{0,1/4,1/2,1,4,8}. The supply Reynolds number is fixed at 100 for the laminar regime and at 5000 for the turbulent one. The second parameter is the ratio of the recess depth versus the film thickness. Six values of this ratio are considered, ranging from 4 (shallow recess) to 152 (deep recess). Detailed pressure patterns on the runner wall are presented in a systematic manner giving a clear insight of the flow effects intervening in the recess and of their mutual interaction. Some effects are explained by analyzing the recirculation zones inside the recess. It is also shown that for certain parameters turbulent flows have qualitatively similar effects as laminar ones but they can also have specific trends. In order to sustain this remark, the pressure variation at the recess downstream end is analyzed in the paper. Finally, the present results and specially the turbulent ones are intended to contribute to the understanding of viscous and inertia effects interactions in a recess flow and to represent a database in view of HJB theoretical modeling.

Impact of the interaction between nitrogen implant and NO anneal on narrow-width transistors

This study reports a new behavior in narrow-width transistors resulting from the interaction of oxides grown with nitrogen implant with the nitridation associated with growing other oxides. Nitric oxide (NO) annealing of 28-/spl Aring/ oxides grown on nitrogen-implanted silicon results in the decrease of NMOS threshold voltage and in the increase (absolute value) of PMOS threshold with decreasing width. This effect arises from the positive charge from NO anneal interacting with the parasitic transistor associated with the shallow trench isolation edge recess. The parasitic impact becomes more pronounced for narrower widths due to higher effect of recess on total transistor width.

An accurate microdisc simulation model for recessed microdisc electrodes

This study concentrates on an accurate determination of the chronoamperometric response for shallow and deep recessed microdiscs. Diffusion to the recessed microdisc is simulated using the finite element method (FEM). The deviation of the chronoamperometric response for a recessed microelectrode from that for the corresponding inlaid microelectrode can be significant depending on the recess depth. This is noted in terms of the magnitude of the chronoamperometric response and the shape of the chronoamperometric curves. We find cottrellian current decay for deep recess microdiscs at short times “switching” to steady-state behaviour at long times. This switch over in behaviour becomes sharper as the depth of the recess increases. The deviation of the recessed microdisc response from previously proposed approximate expressions is also discussed, with emphasis on the significant deviations for shallow recess microdiscs. The simulation model developed here is accurate yielding transient and steady state values. Approximate analytical expressions which can be used to calculate the transient and steady state responses for recessed microdisc electrodes are presented.