Metal Sleeve Research Articles

Bandwidth control of cylindrical ring dielectric resonator antennas using metallic cap and sleeve loading

This study investigates the effect of loading a monopole-fed cylindrical ring dielectric resonator antenna using a metallic cap and metallic sleeve on its top and outer surface, respectively. The proposed design exhibits a considerable shift of its upper cut-off frequency (from 13.8 to 20.5 GHz for top loading and 8.2 to 15.9 GHz for outer-surface loading) with varying inner radii (height) of the metallic cap (sleeve), thereby providing the bandwidth (BW) controllability. Fabricated prototypes were measured and compared with simulations and good agreement was obtained. The measured return loss exhibits the desired BW control without affecting the peak gain and radiation pattern of the antenna, which is also confirmed by the measured radiation patterns. The proposed concept can be used to reconfigure the BW of the antenna according to the user's requirements and improve signal-to-noise ratio by rejecting unwanted frequency bands without employing any additional filter section.

Isolated revision of the acetabular component using alumina-on-alumina bearings without a metal sleeve: A preliminary study.

There has been a debate on the use of ceramic-on-ceramic coupling with the retained femoral stem in isolated acetabular revision. The purpose of this study was to retrospectively review the results and complications of isolated revision of the acetabular component using alumina-on-alumina bearings. Between August 2010 and December 2013, 22 patients (23 hips) with a mean age of 60.74 years (40-73) underwent isolated revision of the acetabular component from metal-on-polyethylene to alumina-on-alumina bearings without using a metal sleeve on the undamaged trunnion. All patients completed clinical and radiographic evaluation. At a mean follow-up of 3 years (2-5.5), all patients had a significant improvement in the clinical outcome, including Harris Hip Score (84.9 vs. 43, p < 0.001), West Ontario McMaster University Osteoarthritis Index Score (14.4 vs. 49.2, p < 0.001), and visual analogue pain score (1.42 vs. 6.63, p < 0.001). Complications included one aseptic loosening of the acetabular component and three noisy hips (click only). No fracture of the ceramic bearings, dislocation, infection, or squeaking noise were observed in any of the patients. Isolated revision of the acetabular component to alumina-on-alumina bearings on the undamaged trunnion may be considered if there is no available titanium sleeves. Our study showed a satisfactory early outcome with minimal complications. However, a longer term follow-up study is necessary.

Bone Loss in Revision Total Knee Arthroplasty: Evaluation and Management.

With the increasing number of total knee arthroplasty (TKA) procedures being performed annually, the burden of revision surgery is also expected to increase. Addressing bone loss during revision TKA is a considerable challenge that requires proper preoperative evaluation and surgical planning. In addition to an assessment of femoral and tibial bone loss, a systematic approach to the management of bone loss associated with TKA includes careful implant selection, adherence to the general principles of revision TKA, and an understanding of the available reconstruction options. These options include cement with screws, morcellized allograft, bulk structural allograft, modular wedges, block augments, porous metal cones or sleeves, and megaprostheses.

Study on Sensitivity of Control Rod Cell Model in Reflector Region of High-Temperature Engineering Test Reactor

The high-temperature engineering test reactor (HTTR) is a block-type high-temperature gas-cooled reactor (HTGR). There are 32 control rods (16 pairs) in the HTTR. Six of the pairs of control rods are located in a core region and the remainder are located in a reflector region surrounding the core. Inserting all control rods simultaneously at the reactor scram in a full-power operation presents difficulty in maintaining the integrity of the metallic sleeve of the control rod because the core temperature of the HTTR is too high. Therefore, a two-step control rod insertion method is adopted for the reactor scram. The calculated control rod worth at the first step showed a larger underestimation than the measured value in the second step, although the calculated results of the excess reactivity tests showed good agreement with the measured result in the criticality tests of the HTTR. It is concluded that a cell model for the control rod guide block with the control rod in the reflector region is not suitable. In addition, in the core calculation, the macroscopic cross section of a homogenized region of the control rod guide block with the control rod is used. Therefore, it would be one of the reasons that the neutron flux distribution around the control rod in control rod guide block in the reflector region cannot be simulated accurately by the conventional cell model. In the conventional cell model, the control rod guide block is surrounded by the fuel blocks only, although the control rods in the reflector region are surrounded by both the fuel blocks and the reflector blocks. The difference of the neutron flux distribution causes the large difference of a homogenized macroscopic cross-section set of the control rod guide block with the control rod. Therefore, in this paper, the cell model is revised for the control rod guide block with the control rod in the reflector region to account for the actual configuration around the control rod guide block in the reflector region. The calculated control rod worth at the first step using the improved cell model shows better results than the previous one.

Microwave ablation of ex vivo bovine tissues using a dual slot antenna with a floating metallic sleeve

Purpose: To study the efficiency of a dual slot antenna with a floating metallic sleeve on the ablation of different ex vivo bovine tissues.Materials and methods: COMSOL Multiphysics® version 4.4 (Stockholm, Sweden), which is based on finite element methods (FEM), was used to design and simulate monopole and dual slot with sleeve antennas. Power, specific absorption rate (SAR), temperature and necrosis distributions in the selected tissues were determined using these antennas. Monopole and dual slot with sleeve antennas were designed, simulated, constructed and applied in this study based on a semi-rigid coaxial cable. Ex vivo experiments were performed on liver, lung, muscle and heart of bovine obtained from a public animal slaughter house. The microwave energy was delivered using a 2.45 GHz solid-state microwave generator at 40 W for 3, 5 and 10 min. Aspect ratio, ablation length and ablation diameter were also determined on ablated tissues and compared with simulated results. Student’s t-test was used to compare the statistically significant difference between the performance of the two antennas.Results: The dual slot antenna with sleeve produces localised microwave energy better than the monopole antenna in all ablated tissues using simulation and experimental validation methods. There were significant differences in ablation diameter and aspect ratio between the sleeve antenna and monopole antenna. Additionally, there were no significant differences between the simulation and experimental results.Conclusions: This study demonstrated that the dual slot antenna with sleeve produced larger ablation zones and higher sphericity index in ex vivo bovine tissues with minimal backward heating when compared with the monopole antenna.

Development and application of inverse heat transfer model between liquid metal and shot sleeve in high pressure die casting process under non-shooting condition

To predict the heat transfer behavior of A380 alloy in a shot sleeve, a numerical approach (inverse method) is used and validated by high pressure die casting (HPDC) experiment under non-shooting condition. The maximum difference between the measured and calculated temperature profiles is smaller than 3 °C, which suggests that the inverse method can be used to predict the heat transfer behavior of alloys in a shot sleeve. Furthermore, the results indicate an increase in maximum interfacial heat flux density (qmax) and heat transfer coefficient (hmax) with an increase in sleeve filling ratio, especially at the pouring zone (S2 zone). In addition, the values of initial temperature (TIDS) and maximum shot sleeve surface temperature (Tsimax) at the two end zones (S2 and S10) are higher than those at the middle zone (S5). Moreover, in comparison with fluctuations in heat transfer coefficient (h) with time at the two end zones (S2 and S10), 2.4-6.5 kW∙m-2∙K-1, 3.5-12.5 kW∙m-2∙K-1, respectively, more fluctuations are found at S5 zone, 2.1-14.7 kW∙m-2∙K-1. These differences could theoretically explain the formation of the three zones: smooth pouring zone, un-smooth middle zone and smooth zone, with different morphologies in the metal log under the non-shot casting condition. Finally, our calculations also reveal that the values of qmax and hmax cast at 680 °C are smaller than those cast at 660 °C and at 700 °C.

Radiological identification of Zweymüller-type femoral stem prosthesis in revision cases.

Since 1979 the number of patients treated with femoral stems has continued to grow, as well as the number of stems with features similar to the Zweymüller prosthesis produced by different companies. Identification can be problematic in case requiring revision. In the present paper, we present an overview of morphometric differences between the different stem designs, which can be useful for radiologic identification in revision cases. By doing some research on the Internet of specialized sites and worldwide literature, we searched for all femoral stems agreeing with Zweymüller principles (cementless, straight, tapered, rectangular cross-sectioned femoral stems). We found 26 different stems from different companies producing or having produced in the past the Zweymüller-type femoral stems for hip prosthesis. Accurate preoperative identification of the Zweymüller femoral stem type may be of critical importance to eventual outcomes following revision surgery. Each manufacturer has different instruments specific to the removal of their primary implants, and ensuring they are available can simplify the revision procedure significantly. Exact pre-operative planning is also necessary for selecting the correct ball head in cases where a stem is well-fixed and can be left in situ. The commonly used notation "Eurocone 12/14" provides no information about the actual taper angle. Whenever the stem is left in situ, the exact specifications of the taper must therefore be obtained from the manufacturer in order to use a metal sleeve that precisely fits it and the ball head. Failure to do so may result in severe complications, such as metallosis. In cases where it is not possible to identify the taper angle, the surgeon may even consider removal of the stem, though this significantly increases the surgical procedure's invasiveness. Only a single, uniform standard taper, such as that offered until 1994 by CeramTec, can solve these issues in the future. The survival rate of the Zweymüller stems after tenyears was 96% and the complication rate was very low. Pre-operative identification of the femoral implant is of considerable importance for planning and correctly implementing revision procedures.

Reliability and Failure Modes of a Hybrid Ceramic Abutment Prototype.

A ceramic and metal abutment prototype was fatigue tested to determine the probability of survival at various loads. Lithium disilicate CAD-milled abutments (n = 24) were cemented to titanium sleeve inserts and then screw attached to titanium fixtures. The assembly was then embedded at a 30° angle in polymethylmethacrylate. Each (n = 24) was restored with a resin-cemented machined lithium disilicate all-ceramic central incisor crown. Single load (lingual-incisal contact) to failure was determined for three specimens. Fatigue testing (n = 21) was conducted employing the step-stress method with lingual mouth motion loading. Failures were recorded, and reliability calculations were performed using proprietary software. Probability Weibull curves were calculated with 90% confidence bounds. Fracture modes were classified with a stereomicroscope, and representative samples imaged with scanning electron microscopy. Fatigue results indicated that the limiting factor in the current design is the fatigue strength of the abutment screw, where screw fracture often leads to failure of the abutment metal sleeve and/or cracking in the implant fixture. Reliability for completion of a mission at 200 N load for 50K cycles was 0.38 (0.52% to 0.25 90% CI) and for 100K cycles was only 0.12 (0.26 to 0.05)-only 12% predicted to survive. These results are similar to those from previous studies on metal to metal abutment/fixture systems where screw failure is a limitation. No ceramic crown or ceramic abutment initiated fractures occurred, supporting the research hypothesis. The limiting factor in performance was the screw failure in the metal-to-metal connection between the prototyped abutment and the fixture, indicating that this configuration should function clinically with no abutment ceramic complications. The combined ceramic with titanium sleeve abutment prototype performance was limited by the fatigue degradation of the abutment screw. In fatigue, no ceramic crown or ceramic abutment components failed, supporting the research hypothesis with a reliability similar to that of all-metal abutment fixture systems. A lithium disilcate abutment with a Ti alloy sleeve in combination with an all-ceramic crown should be expected to function clinically in a satisfactory manner.

Dynamic deformation characteristics of zirconium diboride–silicon carbide under multi-axial confinement

Multiaxial quasi-static and dynamic compression experiments were performed on zirconium diboride-5wt% silicon carbide (ZrB2-5wt%SiC) ceramic composite processed via spark plasma sintering technique. Cylindrical ZrB2–SiC specimens were confined using thick walled metal sleeves to generate various levels of confinement pressure on the lateral surface and then subjected to axial loads under quasi-static and dynamic conditions. Postmortem analysis revealed formation of a macroscopic shear plane in the recovered specimens and slip bands within ZrB2 grains. Compressive strengths of up to 5.6 GPa and 9.8 GPa, respectively, were reached under quasi-static and dynamic strain rates. To capture the strain rate dependent and pressure dependent response the Johnson–Holmquist (JH-2) model was used and relevant parameters were determined for future high velocity impact or shock response simulations utilizing the experimental data generated from low and high strain rate confined compression tests. A comparison of JH-2 model constants for ZrB2–SiC along with other structural ceramics revealed that pressure alone plays a deterministic role in defining the constitutive response of all brittle ceramics including ZrB2–SiC.

Accuracy of a direct drill-guiding system with minimal tolerance of surgical instruments used for implant surgery: a prospective clinical study.

PURPOSEA recently introduced direct drill-guiding implant surgery system features minimal tolerance of surgical instruments in the metal sleeve by using shank-modified drills and a sleeve-incorporated stereolithographic guide template. The purpose of this study was to evaluate the accuracy of this new guided surgery system in partially edentulous patients using geometric analyses.MATERIALS AND METHODSFor the study, 21 implants were placed in 11 consecutive patients using the direct drill-guiding implant surgery system. The stereolithographic surgical guide was fabricated using cone-beam computed tomography, digital scanning, computer-aided design and computer-assisted manufacturing, and additive manufacturing processes. After surgery, the positional and angular deviations between planned and placed implants were measured at the abutment level using implant-planning software. The Kruskal-Wallis test and Mann-Whitney U test were used to compare the deviations (α=.05).RESULTSThe mean horizontal deviations were 0.593 mm (SD 0.238) mesiodistally and 0.691 mm (SD 0.344) buccolingually. The mean vertical deviation was 0.925 mm (SD 0.376) occlusogingivally. The vertical deviation was significantly larger than the horizontal deviation (P=.018). The mean angular deviation was 2.024 degrees (SD 0.942) mesiodistally and 2.390 degrees (SD 1.142) buccolingually.CONCLUSIONThe direct drill-guiding implant surgery system demonstrates high accuracy in placing implants. Use of the drill shank as the guiding component is an effective way for reducing tolerance.

CORR Insights(®): primary ceramic-on-ceramic total hip arthroplasty using a 32-mm ceramic head with a titanium-alloy sleeve.

C eramic-on-ceramic bearings have become a popular alternative to conventional polyethylene in THA. The major advantages of ceramic bearings for THA include their scratch resistance, low coefficient of friction, less-reactive particulate debris, and superior wear resistance. Dating back to the 1970s, ceramic bearing failures were primarily related to aseptic implant loosening and catastrophic ceramic fractures [1]. In the 1990s, a new generation of alumina ceramic bearings became available with higher quality and greater burst strength [3]. They were also mated with implants that had excellent fixation records and high taper tolerances. Despite these advances, ceramic fracture, neck socket impingement, and squeaking remain a current concern. Fracture risk is increased with smaller diameter femoral heads, malpositioned sockets, and the presence of trunnion debris and/or damage. Impingement and squeaking are typically related to implant position, design, and material properties. A more recent concern is the use of larger diameter femoral heads on smaller trunnions. Larger-diameter femoral heads carry a greater risk of fretting corrosion and adverse local tissue responses (ALTRs). Retrievals and in vitro studies [4] have found less fretting corrosion at the head neck junction with ceramic femoral heads compared to metal heads. The addition of a Ti sleeve within the ceramic head decreases the potential risks of fracture from trunnion debris and or damage. However, the metal sleeve raises some concern regarding the potential of fretting corrosion and ALTRs. In the current study, Lim and colleagues reviewed alumina ceramic bearings utilizing a titanium alloy sleeve within the modular ceramic femoral head with a minimum 5-year followup. Currently, clinical studies utilizing alumina ceramic bearings without Ti sleeves have minimum 10-year followup [2, 5]. The principal issues to compare are survivorship revision for any reason, ceramic fracture, and incidence of osteolysis. The authors reported a 97% survivorship for revision for any reason. This is similar to survivorships ranging from 95% to 99% found by others [2, 5]. This CORR Insights is a commentary on the article ‘‘Primary Ceramic-on-Ceramic Total Hip Arthroplasty Using a 32-mm Ceramic Head with a Titanium-alloy Sleeve’’ by Lim and colleagues available at: DOI:10.1007/ s11999-015-4374-y. The author certifies that he, or any member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR or The Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI:10.1007/s11999-0154374-y. J. A. D’Antonio MD (&) Greater Pittsburgh Orthopaedic Associates, 725 Cherrington Parkway, Suite 200, Moon Township, PA 15108, USA e-mail: dantonioja@me.com CORR Insights Published online: 20 June 2015 The Association of Bone and Joint Surgeons1 2015

Optimization of dual slot antenna using floating metallic sleeve for microwave ablation

Backward heating reduction is vital in power distribution optimization in microwave thermal ablation. In this study, we optimized dual slot antenna to yield reduction in backward heating pattern along the antenna shaft with the application of floating metallic sleeve. Finite element methods were used to generate the electromagnetic (EM) field and thermal distribution in liver tissue. The position of the sleeve from the tip of the probe (z = 0 mm) was varied within the range 14 ≤ z ≤ 22 mm while sleeve length was varied within 16 ≤ z ≤ 48 mm at 2 mm interval using operating frequency of 2.45 GHz. The best optimized design has reflection coefficient of −20.87 dB and axial ratio of 0.41 when the sleeve position was at 17 mm and sleeve length was 18 mm. Experimental validation shows that inclusion of a floating metallic sleeve on dual slot antenna for hepatic microwave ablation averagely increased ablation diameter and aspect ratio by 17.8% and 33.9% respectively and decreased ablation length by 11.2%. Reduction in backward heating and increase in power deposition into liver tissue could be achieved by using this antenna to provide greater efficiency and localization of specific absorption rate in delivering microwave energy for hepatic ablation.

Novel method for setting up 3D navigation system with skin-fixed dynamic reference frame in anterior cervical surgery

Purpose: To introduce easy and useful methods using 3D navigation system with skin-fixed dynamic reference frame (DRF) in anterior cervical surgery and to validate its accuracy.Methods: From September 2012 to May 2013, 31 patients underwent anterior cervical surgery and a total of 48 caspar distraction pins were inserted into each cervical vertebra. Every operation was performed using O-arm® navigation system with skin-fixed DRF. To validate the accuracy of these methods, a custom-made metal sleeve was used. In surgical field, through the metal sleeve, the tip of a navigation probe promptly contacts to the tip of caspar pin. We measured the vertical and horizontal distances and the angular deviation in sagittal plane between the caspar pin and the navigation probe on the virtual images and evaluated accuracy of navigation system with skin fixed DRF.Results: Total 31 (males 20, females 11) patients and 48 caspar pins were included in this study. The mean horizontal distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.49 ± 0.71 mm. The mean vertical distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.88 ± 0.93 mm. And the mean angular deviation in sagittal plane between the caspar pin and the navigation probe displayed in navigation monitor was 0.59 ± 0.55°.Conclusions: 3D navigation system with skin-fixed DRF in anterior cervical surgery is a simple and reliable method and it can be a helpful supplement to a spine surgeon’s judgement.

High speed permanent magnet machine design with minimized stack-length under electromagnetic and mechanical constraints

Certain aircraft and military applications require high speed machines with low stack-length and the lowest possible weight. Hence, the accommodation of the highest bore diameter may seem the natural option. However, a rotor design with high diameter results in significant increase in mechanical stresses in the employed magnet retention. In a sleeved magnet retention mechanism, the sleeve thickness can be increased in order to accommodate the stresses. However, this will result is significant drop in air-gap flux-density and will not yield the high power density expected by the machine. This paper presents an analytical technique that combines the sleeve stress model and the air-gap flux density model to calculate the optimal rotor diameter to achieve the maximum power of the machine design for a minimum stack-length. The technique is applied to both a Carbon Fibre sleeve version and a metallic sleeve version. The analytical calculation of the stresses is validated with mechanical finite-element simulations. The machine design with the analytical calculations is validated with electromagnetic finite element simulations. The results confirm the rotor design strategy and the design technique.

Isolated Acetabular Revision With Ceramic-on-Ceramic Bearings Using a Ceramic Head With a Metal Sleeve

The purpose of this study is to evaluate results of isolated acetabular revision with ceramic-on-ceramic bearings using a ceramic head with a metal sleeve. A retrospective review of fifty-three hips was performed. The mean patient age was 49.9years and the mean follow-up period was 5.7years. The mean modified Harris hip score improved from 47.5, pre-operatively, to 84.7 at the time of last follow-up (P<0.001). Two patients reported squeaking of the hip. Three patients experienced loosening cup, necessitating re-revision surgery. There was a significant difference of acetabular bone defect between loose cup group and stable cup group (P=0.018). There were no ceramic fractures and no osteolysis. The survival rate of the acetabular cup at the mid-term follow-up was 94.3%. In conclusion, ceramic head with a metal sleeve can be a reliable option for isolated acetabular revision.

In‐vitro evaluation of the tolerance of surgical instruments in templates for computer‐assisted guided implantology produced by 3‐D printing

The aim of this in-vitro study was to compare the tolerance of surgical instruments in surgical guides produced by 3-D printing, without metal sleeves to a surgical guide with conventional metal sleeves from two different manufacturers. Lateral movements of drill tips caused by tolerance between the sleeve and drill key and between the drill key and the drill were recorded after application of a standardized force to the surgical instruments. Four groups were tested: Control 1 (C1): metal sleeve from commercially available surgical system 1; Test 1 (T1): 3-D-printed sleeve for surgical system 1; Control 2 (C2): metal sleeve from commercially available surgical system 2. Test 2 (T2): 3-D-printed sleeve for surgical system 2. The mean total lateral movement was 0.75 mm (0.5-1.04 mm) in the C1 group and 0.91 mm (0.54-1.34 mm) in the C2 group. The mean amount of movement from tolerance between sleeve and drill-guiding key was 0.31 mm (range 0.22-0.41 mm) in C1 and 0.42 mm (range 0.29-0.56 mm) in C2. This lateral movement was in mean reduced by 0.24 mm (32%) in T1 and by 0.39 mm (43%) in T2 group. This reduction was statistically significant in both groups (P < 0.001). The tolerance of surgical instruments and the lateral movements of the drills were significantly reduced by the use of 3-D printing with reduced sleeve diameter. This reduction could improve the overall accuracy in computer-assisted template-guided implant dentistry. The lateral movement of the drill can be further reduced by using a shorter drill and a higher drill key. This can be considered during implant planning and CAD/CAM of surgical guides.

Comparison of Five-Axis Milling and Rapid Prototyping for Implant Surgical Templates

This study aims to compare and evaluate the accuracy of surgical templates fabricated using coordinate synchronization processing with five-axis milling and design-related processing with rapid prototyping (RP). Master phantoms with 10 embedded gutta-percha cylinders hidden under artificial gingiva were fabricated and imaged using cone beam computed tomography. Vectors of the hidden cylinders were extracted and transferred to those of the planned implants through reverse engineering using virtual planning software. An RP-produced template was fabricated by stereolithography in photopolymer at the RP center according to planned data. Metal sleeves were bonded after holes were bored (group RP). For the milled template, milling coordinates were synchronized using the conversion process for the coordinate synchronization platform located on the model's bottom. Metal bushings were set on holes milled on the five-axis milling machine, on which the model was fixed through the coordinate synchronization plate, and the framework was constructed on the model using orthodontic resin (group CS). A computed tomography image was taken with templates firmly fixed on models using anchor pins (RP) or anchor screws (CS). The accuracy was analyzed via reverse engineering. Differences between the two groups were compared by repeated measures two-factor analysis. From the reverse-engineered image of the template on the experimental model, RP-produced templates showed significantly larger deviations than did milled surgical guides. Maximum deviations of the group RP were 1.58 mm (horizontal), 1.68 mm (vertical), and 8.51 degrees (angular); those of the group CS were 0.68 mm (horizontal), 0.41 mm (vertical), and 3.23 degrees (angular). A comparison of milling and RP template production methods showed that a vector-milled surgical guide had significantly smaller deviations than did an RP-produced template. The accuracy of computer-guided milled surgical templates was within the safety margin of previous studies.

Metal metaphyseal sleeves in revision total knee replacement

Bone loss in the proximal tibia and distal femur is frequently encountered in revision knee replacement surgery. The various options for dealing with this depend on the extent of any bone loss. We present our results with the use of cementless metaphyseal metal sleeves in 103 patients (104 knees) with a mean follow-up of 43 months (30 to 65). At final follow-up, sleeves in 102 knees had good osseointegration. Two tibial sleeves were revised for loosening, possibly due to infection. The average pre-operative Oxford Knee Score was 23 (11 to 36) and this improved to 32 (15 to 46) post-operatively. These early results encourage us to continue with the technique and monitor the outcomes in the long term.

Clamping method improvement for preventing the return hose oil leakage by elastoplastic finite element analysis

The clamping of the return hose to the gearbox pipe end is important to prevent the oil leakage from the automotive hydraulic power steering system. In this context, this paper is concerned with the improvement of the current clamping method using a thin circular steel strip to resolve the oil leakage phenomenon. The clamping of gearbox pipe end and rubber hose by tightening a thin circular steel strip is replaced with the swaging of a circular metal sleeve. For the current and improved clamping methods, the distributions of effective stress, effective strain, and normal contact pressure at the interface between pipe and rubber hose are analyzed and compared by utilizing the elastoplastic finite element analysis. As well, the durability test for verifying the oil leakage-proof performance of the improved method is performed at the level of return hose assembly. It is observed from the numerical analysis and experiment that the return hose oil leakage is successfully resolved by improving the clamping method.

Omnidirectional Circularly Polarized Antenna Combining Monopole and Loop Radiators

In this letter, a new omnidirectional circularly polarized (CP) antenna is proposed. By adopting a coaxial probe, in which a metal sleeve acts as a monopole, and printed spoke-like metal strips fabricated on two substrates, which act as a loop, this antenna exhibits an omnidirectional circularly polarized radiation in the azimuthal plane. Theory, design, simulation, and experiment of the antenna are presented. Measurement results show that the proposed antenna can achieve a -10-dB impedance bandwidth of 13.8% (ranges from 1.55 to 1.78 GHz) and a 3-dB axial-ratio (AR) bandwidth of 17.5% (ranges from 1.46 to 1.74 GHz) in the azimuthal plane. At the frequency of 1.575 GHz, the measured average axial ratio and right-hand CP (RHCP) gain are 1.91 dB and 0.86 dBi, respectively, in the azimuthal plane.