Tube Technique Research Articles

Peritectic solidification mechanism of substantially undercooled liquid Fe-Y-B ternary alloys

Liquid Fe84Y10B6 and Fe74Y16B10 peritectic type alloys were substantially undercooled up to 382 (0.25 TL) and 400K (0.26 TL) with drop tube technique. The molecular dynamics simulation results revealed that the former alloy was characterized by larger Fe, Y and B self-diffusion coefficients and activation energies. In low undercooling regime, γFe phase in Fe84Y10B6 alloy and Y2Fe17Bx phase in Fe74Y16B10 alloy formed preferentially, faceted τ1(Y2Fe14B) phase subsequently developed through peritectic transition. With the increase of undercooling, peritectic transition was promoted by the refined primary phases. Once liquid undercoolings reached certain critical values, a stronger nucleation driving force is provided for τ1 phase, resulting in its direct nucleation and growth by suppressing the formation of primary phases and the following peritectic transformations. If liquid undercooling rose further, there occurred the faceted to non-faceted growth mode transition of the main peritectic τ1 phase. This indicates that high undercooling and rapid solidification is an effective approach to modulate phase transition pathway and microstructural evolution of rare earth alloys.

Dendrite growth kinetics and microstructure evolution mechanism of Ni2TiAl intermetallic compound within substantially undercooled liquid Ni64Al19Ti17 alloy

The dendrite growth kinetics and microstructure evolution mechanism of the Ni2TiAl intermetallic compound within substantially undercooled liquid Ni64Al19Ti17 alloy were investigated using electrostatic levitation (ESL) and drop tube (DT) techniques. The growth velocity of primary Ni2TiAl dendrites displayed a power-law relation with liquid undercooling, achieving a maximum of 80 mm/s at the undercooling of 254 K (0.16 TL). The solidification pathway transformed from primary Ni2TiAl growth plus subsequent (Ni3Ti+Ni2TiAl) eutectic growth into the successive growth of Ni2TiAl and Ni3Ti phases as the alloy undercooling increased sufficiently. The high cooling rates of freely falling alloy droplets effectively suppressed the martensitic transformation observed for primary Ni2TiAl intermetallic compound under typical ESL radiative cooling condition. Both nanoindentation and Vickers hardness performances of the Ni2TiAl phase formed under these two conditions exhibited conspicuous enhancement due to grain refinement effects. The microstructures with martensitic transformation under ESL condition showed higher hardness than those under DT condition despite their larger grain size.

Revisiting the sound absorption mechanisms of a finite flexible perforated panel absorber using a numerical approach.

This study investigates the sound absorption mechanisms of a finite flexible perforated panel absorber. Different from existing work where the mechanisms were often investigated by comparing the sound absorption coefficient curves of different absorber configurations, a numerical approach, called virtual impedance tube (VIT) technique, is developed and used for the analysis. One advantage of this technique is the vast dataset generated can be used to investigate the sound absorption mechanisms from an energy standpoint. The developed VIT technique is first validated using the impedance tube test, where a proportion-integration-differentiation control algorithm is developed to maintain the incident sound at a desired sound pressure level. Then, the sound absorption mechanisms at three absorption peaks, i.e., hole-cavity controlled, panel-cavity controlled, and panel controlled, are investigated and the dominant energy dissipation mechanism at different sound pressure levels (SPLs) is revealed. Finally, an impedance model that takes account of the panel vibration and is applicable to various SPLs is proposed and validated.

Impact of Type and Screen Method on Turnaround Time and Man-Hour Utilization Compared to Conventional Coomb's Crossmatch: A Cross-Sectional Analytical Study.

Background Blood component transfusion is vital for various medical conditions, requiring thorough pretransfusion testing to ensure safety and compatibility. The Type and Screen (T and S) method allows for efficient detection of clinically significant antibodies while reducing unnecessary crossmatching. This study evaluates T and S's impact on turnaround time and man-hour utilization compared to conventional crossmatching. Methodology The study included 835 elective crossmatch requests. Blood grouping, antibody screening, and antihuman globulin (AHG) crossmatching were performed using column agglutination technology, while immediate saline crossmatching was done by tube technique. Turnaround time (TAT), man-hour utilization, and saved rates were calculated for both the T and S protocol and routine AHG crossmatch. Results In this study, 835 elective blood samples underwent antibody screening and immediate saline phase crossmatching, with validation by AHG phase crossmatch. The T and S protocol significantly reduced TAT for both first (51.24 vs. 71.56 minutes) and subsequent transfusions (17.47 vs. 39.67 minutes) compared to AHG crossmatching, with reductions being statistically significant (p < 0.0001). T and S also saved 279.28 man-hours (11.6 man-days), equating to 0.33 man-hours saved per sample. Conclusion Our study shows that the T and S protocol significantly enhances blood bank efficiency by reducing TAT and man-hour utilization compared to conventional AHG crossmatching. This improvement not only optimizes manpower but also makes the process more cost-effective.

An Untargeted Lipidomics Workflow Incorporating High-Resolution Demultiplexing (HRdm) Drift Tube Ion Mobility-Mass Spectrometry.

Global discovery lipidomics can provide comprehensive chemical information toward understanding the intricacies of metabolic lipid disorders such as dyslipidemia; however, the isomeric complexity of lipid species remains an analytical challenge. Orthogonal separation strategies, such as ion mobility (IM), can be inserted into liquid chromatography-mass spectrometry (LC-MS) untargeted lipidomic workflows for additional isomer separation and high-confidence annotation, and the emergence of high-resolution ion mobility (HRIM) strategies provides marked improvements to the resolving power (Rp > 200) that can differentiate small structural differences characteristic of isomers. One such HRIM strategy, high-resolution demultiplexing (HRdm), utilizes multiplexed drift tube ion mobility spectrometry (DTIMS) with post-acquisition algorithmic deconvolution to access high IM resolutions while retaining the measurement precision inherent to the drift tube technique; however, HRdm has yet to be utilized in untargeted studies. In this manuscript, a proof-of-concept study using ATP10D dysfunctional murine models was investigated to demonstrate the utility of HRdm-incorporated untargeted lipidomic analysis pipelines. Total lipid features were found to increase by 2.5-fold with HRdm compared to demultiplexed DTIMS as a consequence of more isomeric lipids being resolved. An example lipid, PC 36:5, was found to be significantly higher in dysfunctional ATP10D mice with two resolved peaks observed by HRdm that were absent in both the functional ATP10D mice and the standard demultiplexed DTIMS acquisition mode. The benefits of utilizing HRdm for discerning isomeric lipids in untargeted workflows have the potential to enhance our analytical understanding of lipids related to disease complexity and biologically relevant studies.

Hattrick of H-deficient phenotypes at a tertiary care health center in India

Abstract: H-deficient phenotypes, commonly known as Bombay blood type, have more inclination to be found in the Indian subcontinent, and conventional gold standard tube techniques are still the recommended method to identify them, provided a strict adherence to testing protocol. There is more to these phenotypes than just the bombay blood type. This brief communication highlights the identification of three H-deficient phenotypes from a single center that adhered to standard operating procedures and basic testing methodologies. It emphasizes the requirement of indirect Coombs test with pooled “O” cells with blood grouping of every sample irrespective of the testing platform and also the H antigen typing on encountering any suspicion. These H-deficient individuals may not be as rare as we assume them to be provided there are reframed testing policies. Although international collaborations and databases like the International Society of Blood Transfusion database have made it easier to record and share knowledge on blood types, a National network and registries of these rare phenotypes are essential to make them available to the general population who actually benefit from them.

Virtually coupled train set control subject to space-time separation: A distributed economic MPC approach with emergency braking configuration

The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set (VCTS) at a minimal but safe distance. To guarantee collision avoidance, the safety distance should be calculated using the state-of-the-art space-time separation principle that separates the Emergency Braking (EB) trajectories of two successive units during the whole EB process. In this case, the minimal safety distance is usually numerically calculated without an analytic formulation. Thus, the constrained VCTS control problem is hard to address with space-time separation, which is still a gap in the existing literature. To solve this problem, we propose a Distributed Economic Model Predictive Control (DEMPC) approach with computation efficiency and theoretical guarantee. Specifically, to alleviate the computation burden, we transform implicit safety constraints into explicitly linear ones, such that the optimal control problem in DEMPC is a quadratic programming problem that can be solved efficiently. For theoretical analysis, sufficient conditions are derived to guarantee the recursive feasibility and stability of DEMPC, employing compatibility constraints, tube techniques and terminal ingredient tuning. Moreover, we extend our approach with globally optimal and distributed online EB configuration methods to shorten the minimal distance among VCTS. Finally, experimental results demonstrate the performance and advantages of the proposed approaches.

A rare case of ABO grouping discrepancy due to probable blood group switching which presented as lost antigens detectable only with indigenous reagents in less sensitive platforms compared to highly sensitive automated platforms using non indigenous reagents

Abstract: Blood group switching in the form of loss or diminished expression of RBC antigens has been reported in malignancies and infections. Blood group antigens are present on the red cell surface. ABO blood group system is the most clinically significant system. Some cases can present as grouping discrepancy. Here we present a rare case of ABO grouping discrepancy due to probable blood group switching which presented as lost antigens detectable only with indigenous reagents in less sensitive platforms compared to highly sensitive automated platforms using non indigenous reagents. 66 year old female whose historic blood group was A Rh D positive with history of uneventful transfusion of 2 units of A Rh D positive packed red cell one and half years back now presented with mycoplasma pneumonia and acute pulmonary edema. On routine complete blood count testing her hemoglobin was 3.6 gm%, request send to blood bank for pretransfusion testing. Testing performed via conventional tube technique and ABO blood group discrepancy was noted with forward grouping turned to be A Rh D positive (positive reaction with anti A1 lectin) and on reverse grouping 3+ reactions was observed in both A and B cell giving a picture of O blood group. Blood grouping was performed in different platforms including fully automated, semi automated and manual using commercially available antisera and human plasma as a source of anti A, anti B antibodies for forward grouping. The antisera used in automated platforms are non indigenous and that for manual are indigenous. Discrepancy was noted (Forward A and Reverse O) in CTT with commercially available antisera and human plasma as reagents for forward grouping .The same discrepancy was noted with CAT in neutral card with commercially available antisera for manual grouping. But when grouping performed with Column Agglutination Technology using matrix grouping gel card the discrepancy was resolved reporting the blood group as O. For further confirmation we repeated the blood grouping in another fully automated platform, SPRCA Technology (Immucore NEOIRIS) and in that also no discrepancy noted giving a picture of O group. This patient probably had undergone a blood group switching from A to O by losing some but not all A epitopes and started anti A antibody production. Some A epitopes which were not lost had been picked up by the commercially available antisera intended for manual grouping. These antisera are indigenous in origin. Also when human plasma was used as source of antibodies the A epitopes which were not lost were detected. But when grouping was done with non-indigenous antisera in both manual and automatic platform the A epitopes were not detected. This case points towards the relevance of incorporating indigenous antisera in automated platforms.

Effects of K excess in microstructure of (Ba0.6K0.4)Fe2As2 superconducting powders

Abstract Iron-based superconductors (IBSs) are promising for high-field applications due to their exceptional characteristics, like ultrahigh upper critical field and minimal electromagnetic anisotropy. Creating multifilamentary superconducting wires with elevated transport critical current density is essential for practical use. The Powder in Tube (PIT) technique is commonly used for this purpose, but achieving optimal results requires careful exploration of powder microstructural properties. This is particularly crucial for superconductors like (Ba,K)122, the IBS most promising from an applicative point of view, where factors such as reactivity, volatility, and toxicity of constituent elements affect phase formation. Potassium volatility often leads to nonstoichiometric conditions, introducing excess potassium in the formulation. This study focuses on the impact of potassium excess δ on the microstructural properties of the ‘optimally doped’ (Ba0.6K0.4+δ )Fe2As2 phase (0 ⩽ δ ⩽ 0.08). Using techniques like Scanning Electron Microscopy, x-ray diffraction, and temperature-dependent magnetization measurements, we demonstrate the ability to produce nearly pure powders of the superconducting phase with controlled grain size. Our findings are relevant for PIT wire fabrication, where grain size strongly affects mechanical deformation. Grain size also influences transport properties, as observed in previous studies, where reducing grain size enhanced current-carrying capability at high magnetic fields.

Stability of immunohaematological reagents used for blood typing of recipients in the tube technique.

The storage temperature of immunohaematological reagents generally ranges from 2 to 8°C, and they should be utilised at room temperature. This study aimed to analyse the stability of immunohaematological reagents used in ABO and RhD typing. The evaluation encompassed the potency, specificity, and integrity of anti-A, anti-B, anti-D, RhD control sera, and A1 and B red blood cells (RBC) reagents after long (8 h) and short (4 h) daily periods of exposure to room temperature (20-24°C), 5 days a week for 4 weeks. Additionally, the A1 and B RBC reagents were exposed daily for 11 h and 30 min at room temperature, including 30 more minutes at room temperature with simultaneous homogenisation through equipment. For the control, an aliquot of each reagent was constantly stored at refrigeration temperature, while another was exposed to room temperature for 12 h daily. Tests conducted included reaction intensity, titration, and avidity for antisera, reaction intensity, free haemoglobin determination, and electrical conductivity for the RBC reagents. The antisera maintained the reaction intensity. The titre and avidity of the antisera satisfied the minimum Brazilian requirements after different exposure periods. A higher free haemoglobin concentration was noted in the RBC reagents subjected to room temperature and simultaneous homogenisation, although this did not affect the potency and specificity. The electrical conductivity average of the RBC reagent remained consistent. The findings indicate that the immunohaematological reagents from a specific manufacturer are stable under the tested temperature, ensuring the quality of the results under these conditions.

Realization of a shock-tube facility to study the Richtmyer-Meshkov instability driven by a strong shock wave.

A shock-tube facility capable of generating a planar shock with the Mach number higher than 3.0 is developed for studying Richtmyer-Meshkov instability induced by a strong shock wave (referred to as strong-shock RMI). Shock enhancement is realized through the convergence of shock within a channel with the profile determined by using shock dynamics theory. The facility is designed considering the repeatability of shock generation, transition of shock profile, and effects of viscosity and flow choking. By measuring the dynamic pressure of the tube flow using pressure sensors and capturing the shock movement through the high-speed shadowing technique, the reliability and repeatability of the shock tube for generating a strong planar shock are first verified. Particular emphasis is then placed on the ability of the facility to study strong-shock RMI, for which a thin polyester film is adopted to form the initial interface separating gases of different densities. The results indicate that the shock tube is reliable for conducting strong-shock RMI experiments.

Harnessing the potential of blood donors negative for high prevalence Rh antigens: A database initiative for thalassaemia care

Background and objectivesWith increasing life expectancy and prevalence of thalassaemia, it has led to a greater need for safe blood, yet the current supply from voluntary donors is insufficient to meet this demand. Thalassaemia recipients face a significant risk of alloimmunization because of repeated exposure to foreign red cell antigens. Study aims to determine high prevalent Rh antigen negative donors in western India donor population along with what percentage of these donors are willing to become dedicated voluntary donors for thalassaemia patients. Study also aims to examine factors influencing their willingness and challenges faced in mobilizing dedicated donors. Method700 whole blood donors from western India, following screening for inclusion & exclusion criteria as per Drugs and Cosmetic Act (DCA) 2020 amendment guidelines & were sero-negative for transfusion transmitted infections were enrolled for the study. Red cell phenotyping was performed using Conventional Tube Technique (CTT) for “D”, “C”, “E”, “c”, “e” and “K” antigen using known antisera. Donors that were “C” AND/OR “e” antigen negative were contacted telephonically and were counseled and motivated for becoming voluntary blood donors. Statistical analysis assessed correlation between donation frequency, donor’s occupation and education. ResultAmong 700 donors, 96.6% (n = 676) were males and 3.4% (n = 24) were females. The most predominant blood group was B > O > A > AB. Rh(D) antigen was present in 91.44% (n = 640) and absent in 8.6% (n = 60). Prevalence of other Rh antigens is as follows: “e” (99%) > “C” (85.4%) > “c” (59.1%) > “E” (18.0%). Only 1.15% had “K” antigen positive. The commonest Rh phenotype R1R1 (DCe/DCe) was expressed by 40.57% (n = 283), and the least common r″r (cE/ce), r″r″ (cE/cE) and r′r′ (Ce/Ce) was found in 0.14% (n = 1), respectively. ‘C’ negative, ‘e’ negative, ‘C’ and ‘e’ antigen negative donors constituted 14.8% (n = 104) with 93.2% (n = 97) C-antigen negative, 1.92% (n = 2) e-antigen negative and 4.8% (n = 5) both “C” and “e” antigen negative donors. The commonest phenotypes among C-antigen and e-antigen negative donors were rr (50%) and RzR2 (1.94%) respectively. Likewise, the most common phenotype amongst both C- and e-antigens negative donors was R2R2 (3.84%). 61.5% of the donors agreed to enroll for voluntary blood donation following telephonic invitation, while 6.8% of them refused permanently. Approximately, 3.9% of the blood donors were willing to donate blood only when needed and 27.8% of them could not be contacted. ConclusionCreating a database of voluntary donors with known phenotype, especially who lack very common antigens like “C” and “e” and are willing to become dedicated, regular voluntary donors for thalassemic patients can ensure timely administration of safe blood. One of the major challenges for this noble initiative was lack of awareness which can be circumvent effectively with proper counseling efforts.

Effect of CSET processing on a commercial purity polycrystalline Al sample and numerical simulation of induced plastic deformation

A commercial purity Al sample was processed using complex shearing of the extruded tube (CSET) technique, which enables the preparation of tubes from bulk samples in one step by combining extrusion and two Equal Chanel Angular Pressing - like passes. In the present paper, the CSET process was simulated and analysed using Finite Element Method. The results of the simulations were compared with the experimental findings. Both modelling and experiment revealed a gradual increase in plastic deformation in the material during CSET processing. Simultaneously, microscopic investigations confirmed concurrent grain refinement. Moreover, a slight gradient of plastic deformation predicted by FEM in the main deformation zone was confirmed by microhardness measurements. In the resulting tube wall, electron backscattered diffraction experiments revealed the presence of fine grains and a partially recovered microstructure. The Vickers microhardness was found to be doubled by the CSET processing.

Blood cross-matching using gel card technique compared to conventional tube technique: A diagnostic evaluation study

Abstract Background: Conventional tube technique (CTT) is the most commonly used method for blood cross-matching in India. The gel card technique is the latest technique emerged and due to its accurate results, it is considered a method of choice for cross-matching. Objective: The objective of the study was to compare blood cross-matching using the gel card technique compared to CTT with and without anti-human globulin (AHG). Materials and Methods: A diagnostic evaluation study was conducted on 1500 blood samples. Patients’ blood samples were sent to the blood bank for routine cross-matching procedures. Both tube and gel techniques were used for Coombs cross-matching and their results were compared and analyzed. Results: In our study, males were slightly more than females. The most common indication for blood transfusion was associated with medical conditions (28.4%). The gel card technique was as accurate as CTT with AHG. It was 100% sensitive and specific. At the same, the positive predictive value (PPV) and negative predictive value (NPV) are also 100%. The CTT sensitivity was 98.99% and it was 100% specific. The PPV was also 100% but the NPV was only 37.5% which means that the false-positive rate was very high with CTT compared to CTT with AHG. Because CTT without AHG in present study showed more false positive results as compared to gel matrix. The average time required for a single compatibility test by gel card method was 25 ± 3.5 min, while that for CTT with AHG was 90 ± 4.9 min (indirect antiglobulin test [IAT]) and 30 ± 3.8 min if IAT was not done. Thus, even though CTT with AHG was equally effective as that of the gel card method, but time taken was significantly more (P &lt; 0.05). Conclusion: The gel technique has definite advantages over the tube technique because of being able to give more accurate results, less chances of false-positive and false-negative results, interpretation of results more objective consistent and reproducible, and its shorter duration for cross-matching. However, in developing countries like India, the gel technique if applied widely, costs factor would come down and could be considered a better alternative to CTT to ensure successful transfusion.

Impact of flexible vegetation on hydraulic characteristics in compound channels with converging floodplains

ABSTRACT Floodplains in natural rivers are curved and narrow, rather than following a straight path and the presence of vegetation and varying depth of flow affects the flow parameters of the channels. The purpose of this study is to investigate the effects of the convergence of the channel and relative depth of flow on the depth-averaged velocity (DAV) and boundary shear stress (BSS) of a converging compound channel. The effect of vegetation on DAV and BSS was also deliberated. To examine the effect of vegetation, synthetic grass 8 cm in height was used as a flexible vegetation to depict the natural conditions of the rivers. The DAV was calculated using an acoustic Doppler velocimeter (ADV) and the measurement of BSS was done using the Preston tube technique. After analysing the data, it was revealed that as the convergence of floodplains increases, maximum DAV increases. The presence of vegetation reduces the velocity specifically at lower flow depths. BSS increases with the convergence as well as vegetation. This research provides valuable data and results which will be helpful in better flood management, river restoration, and designing effective hydraulic structures.

Laminar burning velocities of Ethanol-air mixtures at elevated temperatures using the tube method

Abstract— Experiment test for premixed laminarcombustion of ethanol-air mixtures has been conducted in a tube technique. The laminar burning velocities of premixedhomogeneous Ethanol fuel and air mixtures are determinedover a wide range of equivalence ratio at elevatedtemperatures. The experimental apparatus has beenmodified for apprehension of flame behaviors at 340 K withboth ends open to the atmosphere. For each of the flamespeeds, unburned gas velocities and flame surface areashave been measured and computed to determine burningvelocity. Repeatable and reliable experimental data areobtained in this rig, showing good agreements with previousdata. Laminar burning velocities are increased with elevatedtemperatures.

PEMBUATAN PADUAN INTERMETALIK Mg2Si DENGAN DOPING BISMUTH SEBAGAI MATERIAL TERMOELEKTRIK

Increasing efficiency in gasoline fuel consumption in motorized vehicles is currently continuing. One way this is done is by making use of the energy that is lost during the combustion of a motorcycle engine. About half of the energy produced during burning will be lost due to heat energy and exhaust gases. This waste heat can be utilized by converting it into another form of energy. Thermoelectric materials are those that can convert heat energy into electricity directly. Thus, in this work, we synthesized the bismuth-doped Mg2Si thermoelectric material using a solid-state reaction method using a powder in a sealed tube technique. The initial step in the production process involves measuring the raw materials bismuth, silicon, and magnesium using the Mg2Si1-xBix formula (x = 0.00, 0.025, and 0.045). The raw material powder is grinded in a shaker mill before being sealed in a stainless steel tube. The powder is sealed in a tube and heated to 800 °C for 6 hours. According to XRD test results, the Mg2Si phase and Si and MgO phases have formed. The lattice constant of the cubic Mg2Si phase was found at ~0.636 nm. A SEM investigations of surface morphology suggest that bi-doping on Si sites influences grain size refinement. Therefore, it can be concluded that the Mg2Si intermetallic alloy production process was successfully completed.

Anti-A and anti-B titers in A, B and O whole blood donors: Beyond “dangerous O”

Background and ObjectivesHemolytic transfusion reactions (HTRs) pose significant risks in transfused patients, with anti-A and anti-B antibodies in donor plasma being potential contributing factors. Despite advancements in component preparation, HTRs remain a concern, particularly with apheresis-derived platelets. This study aimed to determine the prevalence of high anti-A and anti-B titers among A, B, and O blood group donors and to explore factors associated with high titers. Materials and MethodsA cross-sectional observational study was conducted over 18 months, enrolling 978 participants from a tertiary care teaching hospital in Western India. Anti-A and anti-B titers were determined using the Conventional Tube Technique (CTT). Statistical analysis assessed correlations between high titers and demographic factors. ResultsThe majority of participants were young males (98.8%). Prevalence of high titers for IgM anti-A was 12.2% and IgG anti-A was 2.5%. For anti-B, IgM titers were 2.3% and IgG titers were 0.2%. The prevalence of dangerous O was found to be 14.1%, while 3.52% and 10.5% of A and B blood group donors were found to have high titers, respectively. Factors associated with high titers included female gender, vegetarian diet, age <30 years, and O blood group. ConclusionThe study sheds additional light and provides supplementary information regarding the prevalence and correlation of high anti-A and anti-B titers among O, A and B blood donors. Understanding these factors is crucial for optimizing transfusion safety protocols, including selective screening of platelet units and tailored transfusion strategies based on donor characteristics.

Green sound-absorbing material prepared by using natural fiber for building acoustics

Natural fibers are recently seen as a replacement for synthetic fibers as core material to produce sound-absorbent materials. These are biodegradable and renewable, and using them as sound-absorbent material brings many environmental benefits as it is much greener compared to existing inorganic and synthetic fibers. Present exploration serves the purpose of investigation and comparison of the acoustic absorption characteristics of individual and mixed natural fibers; jute, coconut coir, and bamboo. Each fiber is reinforced with natural rubber in a certain weight ratio during the fabricating stage. The fibers are then compressed with the help of mould and ram piston in a hydraulic press. The compression is done in the form of cylindrical samples of 40 mm diameter. Each specimen is kept 36 mm thick, according to the given standards. The impedance tube technique is used to evaluate acoustical performances. Multilayered composites made of layers of coir, jute, and bamboo performed better in all the frequency ranges than composites made of individual fibers. Results establish that these fibers are promising and a viable option for light and environment-friendly sound absorption materials.

Optimization design of an innovative francis draft tube: Insight into improving operational flexibility

Hydropower has transitioned from base-load generation into an energy regulator in the hydro-wind-solar integrated systems, resulting in prolonged turbine operation under off-design conditions. Inspired by the new requirements of operation mode, an innovative Francis draft tube with inclined conical diffuser is presented to mitigate the pressure fluctuations and fatigue damage induced by flow instabilities. The design is optimized and comprehensively investigated to improve the operational flexibility. Computational fluid dynamics combined with design of experiments, artificial neural network and multi-objective optimization process lead to two optimal designs denoted as Opt-1 and Opt-2 from the Pareto fronts. Corresponding maximum pressure fluctuation amplitude is reduced by 15 % and 20 % compared to the traditional, respectively. An 81 % decrease of the fluctuating pressure recovery for the modified draft tube is obtained, leading to a steadier runner torque and consequently lower power swing. The asymmetric design of inclined daft tube is mainly targeted at the mitigation of the synchronous component as well as the attenuation of interaction between the swirling flow and elbow, accompanied with the mitigated energy of first-order vortex structure. The proposed innovative draft tube and optimization technique are found useful to broaden the operating range of hydraulic turbine in a computationally affordable way.