Titanium machining with new plasma boronized cutting tools

Titanium is a commonly used material in various critical applications such as aerospace and biomedical applications. In this article, for the first time in the literature, development and implementation of a novel plasma boronizing process on Tungsten Carbide (WC) cutting tools is introduced. Plasma boronizing on WC tools is performed with gas combination of 10% BF₃, 40% Argon and 50% H₂ at different temperatures and durations. Performance enhancements of plasma boronized WC tools on Titanium (Ti-6Al-4V) machining are investigated under various cutting conditions. It is found that new plasma boronizing of WC is a very cost effective solution for significantly increasing tool life in Titanium machining.     

Adaptive wave cancelation by acceleration feedback for ramp-connected air cushion-actuated surface effect ships

We solve the problem of cargo transfer in high sea states over a ramp from a large, medium-speed, roll-on/roll-off (LMSR) vessel to a smaller connector vessel of a surface effect ship (SES) type. Our aim is to reduce ramp motion between the LMSR and SES in order to provide a safer environment for cargo transfer. We design an air cushion actuated controller to estimate and cancel the wave disturbance and stabilize the heave of the SES via heave acceleration feedback with actuation of the louver area for the case where the hydrodynamic and other parameters of the SES are not known a priori and the pressure dynamics of the air cushion contains nonlinearly parameterized unknown terms. We demonstrate the effect of our control design in simulations in a time-domain seakeeping code, named AEGIR.     

Numerical study of effect of oxygen fraction on local entropy generation in a methane-air burner

This study considers numerical simulation of the combustion of methane with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio (Φ) and oxygen percentage (γ ) on combustion and entropy generation rates are investigated for different Φ (from 0.5 to 1.0) andγ values (from 10 to 30%). Combustion is simulated for the fuel mass flow rate resulting in the same heat transfer rate (Q)y to the combustion chamber in each case. Numerical calculation of combustion is performed individually for all cases with the use of the Fluent CFD code. Furthermore, a computer program has been developed to calculate the volumetric entropy generation rate and the other thermodynamic parameters numerically by using the results of the calculations performed with the FLUENT code. The predictions show that the increase of Φ (or the decrease of λ) significantly reduces the reaction rate levels. Average temperature in the combustion chamber increases by about 70 and 35% with increase ofγ (from 10 to 30%) and Φ (from 0.5 to 1.0) respectively. With increase ofγ from 10 to 30%, volumetric local entropy generation rate decreases by about 9 and 4% for Φ = 0.5 and 1.0 respectively, while total entropy generation rate decreases exponentially and the merit numbers increase. The ratio of the rates useful energy transfer to irreversibility therefore improves as the oxygen percentage increases     

Persistent left superior vena cava: Two case reports and a review from nephrologists’ perspective

Thoracic venous anomalies without congenital heart anomalies are present in minority of the population, but they are frequent enough to be encountered while placing hemodialysis catheters through the jugular or subclavian veins. Persistent left superior vena cava is the most commonly seen anomaly and it is rarely noticed before the observation of an unusual course of hemodialysis catheter or guidewire on chest X‐ray. We present two patients with previously unspotted persistent left superior vena cava and uncomplicated hemodialysis catheter insertions through the internal jugular veins with good catheter functions. Review of the relevant literature from a nephrologists’ perspective with technical aspects is provided.     

State derivative feedback for adaptive cancellation of unmatched disturbances in unknown strict-feedback LTI systems

Solutions exist for the problem of canceling sinusoidal disturbances by the measurement of the state or by the measurement of an output for linear and nonlinear systems. In this paper, an adaptive backstepping controller is designed to cancel sinusoidal disturbances forcing an unknown linear time-invariant system in controllable canonical form which is augmented by a linear input subsystem with unknown system parameters. The state-derivatives of the original subsystem and the state of the input subsystem are the only measurements that are used in the design of the controller. The design is based on four steps, (1) parametrization of the sinusoidal disturbance as the output of a known feedback system with an unknown output vector that depends on unknown disturbance parameters, (2) design of an adaptive disturbance observer for both disturbance and its derivative, (3) design of an adaptive controller for the virtual control input, and (4) design of the final adaptive controller by using the backstepping procedure. It is proven that the equilibrium of the closed-loop adaptive system is stable and the state of the considered original subsystem converges to zero as t→∞$t\to \infty$ with perfect disturbance estimation. The effectiveness of the controller is illustrated with a simulation example of a third order system.     

Investigating the effects of draw ratio,hot-pin temperature,and overfeeding on the color values of air-jet textured polyester yarns

In this study, influence of draw ratio, hot-pin temperature, and overfeeding on the color values of air-jet textured yarns, which were produced from polyester partially oriented yarn, was investigated. Two different air-jet textured yarns were produced by setting the value of only one variable to its minimum and maximum, while the reference values selected for the production of the reference yarn were used for the rest of the variables. Six different air-jet textured yarns, which were produced by varying draw ratio, hot-pin temperature, and overfeeding, and the reference air-jet textured yarn were dyed with the same dyeing procedure. Some physical properties such as linear density, tenacity, and breaking extension of the air-jet textured yarns were measured and images of the cross-section of the yarns were taken. The color coordinates of the dyed yarn samples were also measured. The color differences of six yarn samples compared to reference air-jet textured yarn were calculated. Changing draw ratio, hot-pin temperature, and overfeeding affected the color values of the air-jet textured yarns according to the results. It was found that, overfeeding is the parameter that affects the color values of the air-jet textured yarn most.