Not Breathing During the Approach Phase Ameliorates Freestyle Turn Performance in Prepubertal Swimmers

This study compared the effects of two breathing conditions during the freestyle turn approach phase in swimmers. Thirty-four prepubertal swimmers (mean ± SD: 10.59 ± 0.97 years) were divided into two groups: No Breath (NB), not breathing at the last stroke, and Breath Stroke (BS). Swimmers performed three turns with 5 min of rest between the repetitions. Kinematic parameters were recorded with two underwater and two surface cameras. Total turn time (NB: 9.31 ± 1.34 s; BS: 10.31 ± 1.80 s; p = 0.049), swim-in time (NB: 3.89 ± 0.63 s; BS 4.50 ± 0.79 s; p = 0.02) and rotation time (NB: 2.42 ± 0.29 s; BS: 3.03 ± 0.41 s; p = 0.0001) were significantly shorter and swim-in distance [NB: 0.70 (0.58,0.77) m; BS: 0.47 (0.34,0.55) m; p = 0.0001], glide distance (NB: 1.06 ± 0.21 m; BS: 0.70 ± 0.20 m; p = 0.0001) and surfacing distance [NB: 1.79 (1.19,2.24) m; BS: 1.18 (0.82,1.79) m; p = 0.043] were significantly longer in NB than in BS. Moreover, speed-in (NB: 1.04 ± 0.14 m/s; BS: 0.93 ± 0.14 m/s; p = 0.031) and push-off speed (NB: 2.52 ± 0.30 m/s; BS: 1.23 ± 0.20 m/s; p = 0.001) were significantly higher in NB than in BS. Swim-in time was positively and negatively correlated with rotation time and glide distance, respectively, whilst negative relationships between total turn time and swim-in distance, total turn time and surfacing distance and total turn time and speed-in were found. Our study showed that in prepubertal swimmers not breathing at the last stroke during the approach phase positively affected kinematic parameters of the turn, allowing to approach the wall faster, rotate the body quicker, increase push-off speed, reduce turn execution time, thus improving overall turn performance.

A multi-item manufacturing system with an outsourcer and random defective items

This study examines a multi-item manufacturing problem with a single machine, an outsourcer, and random defective items. To cope with the increasing multi-product demands from global markets, modern manufacturing firms must make an efficient production plan to satisfy customer’s needs with quality goods and smooth the in-house fabrication schedule and utilization. Outsourcing is an effective option to avoid machine overloads and smooth fabrication schedules. Further, the fabrication of random defective products is inevitable because of unanticipated factors in real manufacturing environments. These products must be identified, separated and discarded to retain the desired quality of the finished lot. To address the above-mentioned concerns, this study develops a mathematical model to represent a hybrid stock refilling system, employs mathematical derivations to find long-run average system expenses, and uses an optimization technique to derive a closed-form common rotation time for this hybrid system. The results of this study show the individual and combined impacts of variations in outsourcing percentages and scrap rates on optimal rotation time and diverse core system parameters (such as machine utilization, specific cost component, etc.) to facilitate planning, controlling, and decision making in such a particular hybrid fabrication system.

TAGUCHI-BASED OPTIMIZATION OF HEAD AND NECK CT ANGIOGRAPHY: IN-VIVO ENHANCED TRIGGERED TIMING FOR 600 PATIENTS

The Taguchi-based optimization of head and neck CT angiography (CTA) using in-vivo enhanced triggered timing for 600 patients was accomplished in this study. A total of 600 patients were categorized into three (test, verification, and implementation groups with 360, 120, and 120 patients, respectively). The patients in the test group were randomly assigned into 18 sub-groups according to Taguchi L[Formula: see text](2[Formula: see text]) orthogonal array for optimizing factor combinations of head and neck CTA. The signal-to-noise ratio was defined as a high LRA/US ratio (both left and right arterial pressure divided by upper sinuses’ one) and low stdev. The seven factors of CTA were: (A) left- or right-hand injection; (B) tube current, mA; (C) kilovoltage peak, kVp; (D) contrast media concentration; (E) FOV; (F) flow rate of contrast media; and (G) rotation time for one CTA loop. With the Taguchi unique organization, 18 sub-groups (each containing 20 patients’ real LRA/US ratios) could cover 1458 cases and provide the appropriate reliability. The optimal factor combination was identified as follows: (A) left-hand injection, (B) tube current of 280[Formula: see text]mA, (C) 100[Formula: see text]kVp, (D) contrast media concentration of 60%, (E) FOV of 250[Formula: see text]mm, (F) contrast media flow rate of 4.0[Formula: see text]ml/s, and (G) rotation time for one CTA loop of 0.9[Formula: see text]s. The optimal suggestion was validated in the verification group with 120 patients and applied to the implementation group with 120 patients. The successful factor combination is instrumental in defining a standard protocol for medical staff in deriving the maximal LRA/US value ([Formula: see text]) of head and neck CTA.

Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

We study symmetries of open bosonic systems in the presence of laser pumping. Non-Hermitian Hamiltonians describing these systems can be parity-time ($${{\mathscr{PT}}}$$ PT ) symmetric in special cases only. Systems exhibiting this symmetry are characterised by real-valued energy spectra and can display exceptional points, where a symmetry-breaking transition occurs. We demonstrate that there is a more general type of symmetry, i.e., rotation-time ($${\mathscr{RT}}$$ RT ) symmetry. We observe that $${\mathscr{RT}}$$ RT -symmetric non-Hermitian Hamiltonians exhibit real-valued energy spectra which can be made singular by symmetry breaking. To calculate the spectra of the studied bosonic non-diagonalisable Hamiltonians we apply diagonalisation methods based on bosonic algebra. Finally, we list a versatile set rules allowing to immediately identifying or constructing $${\mathscr{RT}}$$ RT -symmetric Hamiltonians. We believe that our results on the $${\mathscr{RT}}$$ RT -symmetric class of bosonic systems and their spectral singularities can lead to new applications inspired by those of the $${{\mathscr{PT}}}$$ PT -symmetric systems.

A two-dimensional half-space problem in an initially stressed rotating medium with microtemperatures

PurposeThe purpose of this paper is to establish a model of two-dimensional half-space problem of linear, isotropic, homogeneous, initially stressed, rotating thermoelastic medium with microtemperatures. The expressions for different physical variables such as displacement distribution, stress distribution, temperature field and microtemperatures are obtained in the physical domain.Design/methodology/approachNormal mode analysis technique is adopted to procure the exact solution of the problem.FindingsNumerical computations have been carried out with the help of MATLAB programming, and the results are illustrated graphically. Comparisons are made to show the effects of rotation, time and microtemperatures on the resulting quantities. The graphical results indicate that the effects of rotation, microtemperatures and time are very pronounced on the field variables.Originality/valueIn the present work, we have investigated the effects of rotation, time and microtemperature in an initially stressed thermoelastic medium. Although various investigations do exist to observe the disturbances in a thermoelastic medium under the effects of different parameters, the work in its present form, i.e. the disturbances in a thermoelastic medium in the presence of angular velocity, initial stress and microtemperature have not been studied till now. The present work is useful and valuable for analysis of problems involving coupled thermal shock, rotation parameter, microtemperatures and elastic deformation.

OPTIMIZING THE MINIMUM DETECTABLE DIFFERENCE OF COMPUTED TOMOGRAPHY SCANNED IMAGES VIA THE TAGUCHI ANALYSIS: A FEASIBILITY STUDY WITH AN INDIGENOUS HEPATIC PHANTOM AND A LINE GROUP GAUGE

Objective: The minimum detectable difference (MDD) of computed tomography (CT) scanned images was quantified and optimized according to an indigenous hepatic phantom, line group gauge and Taguchi [Formula: see text] optimization analysis in this work. Methods: Optimal combinations of CT scan factors in every group with the level organization were judged using the Taguchi analysis, in which every factor was organized into only 18 groups, creating evaluated outcomes with the same confidence as if every factor was analyzed independently. The five practical factors of the CT scan were (1) kVp, (2) mAs, (3) pitch increment, (4) field of view (FOV) and (5) rotation time for one loop of CT scan. Insofar as each factor had two or three levels, the total number of 162 (i.e., [Formula: see text]) combinations was considered. Results: The optimal setting was 120[Formula: see text]kVp, 300[Formula: see text]mAs, 0.641 pitch, 320[Formula: see text]mm FOV and 1.0[Formula: see text]s of rotation time of CT scan. The minimal MDD was 2.65[Formula: see text]mm under 0.39[Formula: see text]mm of the slit depth from the revised Student’s [Formula: see text]-test with a 95% confidence level. In contrast, the MDD of conventional and the best one (no. 7) among all original 18 groups were 3.27[Formula: see text]mm and 2.93[Formula: see text]mm for 0.43[Formula: see text]mm and 0.41[Formula: see text]mm slit depths, respectively. Conclusion: The Taguchi analysis was found very lucrative for the design of imaging analysis in practical diagnosis. The indigenous line group gauge and hepatic phantom also proved to be suitable in simulating the human body in real hepatic carcinoma examination.