Periodic Interruption Research Articles

Finite element simulations of free reed instrument operation

To facilitate research into the acoustical properties of free reed instruments, there is a need for a quick and inexpensive way to prototype new geometries. It is here that a computational model with easily adjustable parameters offers a substantial advantage over an experimental apparatus if it can sufficiently resolve the essential acoustic features. Simulations using the finite element method have been utilized to solve the fluid dynamics, pressure acoustics, structural mechanics, and the multi-physics couplings underpinning various free reed systems. These phenomena include attack transients and frequency-pressure dependence of Western free reeds, fluid-structure interaction of turbulent airflow in an Asian free reed, effects of air compressibility on reed vibration, and the acoustic impedance of a reed-driven khaen pipe. Results consistent with experimental and analytical models were obtained and methods of optimizing the computational cost while maintaining realism are proposed. The models fail, however, to capture the essential feature of free reed sound production via the periodic interruption of airflow through the reed plate. Ways for future research to achieve this benchmark are suggested. [Research supported by National Science Foundation, Grant NSF-REU-1950337.]

Inter-element variation in the bone histology ofAnteosaurus(Dinocephalia, Anteosauridae) from theTapinocephalusAssemblage Zone of the Karoo Basin of South Africa

Despite its abundance in the Permian fossil record of South Africa, little is known about the life history of Anteosaurus. Here we examine the bone microstructure of multiple skeletal elements of Anteosaurus from the Tapinocephalus Assemblage Zone of the Karoo Basin. The bone histology of Anteosaurus magnificus reveals that the cortex is composed of highly vascularized, uninterrupted fibrolamellar bone tissue surrounding the inner spongy medullary region. However, the histology of two ribs and a previously described femur of another Anteosaurus taxon revealed an interrupted growth pattern with lines of arrested growth and peripheral rest lines occurring in the compacta, indicating periodic pauses in growth possibly linked to the slowing down of growth during maturity. Given that the fibula of the same individual has well-vascularised fibrolamellar bone tissue without any growth marks in the cortex; this suggests variation in skeletal growth. Based on our histological results, three growth dynamic stages are deduced for the genus Anteosaurus: (i) the earliest growth stage is represented by the predominance of highly vascularized, uninterrupted fibrolamellar bone tissue in the inner cortex, which suggests rapid periosteal bone deposition during early ontogeny; (ii) the next stage of growth shows periodic interruptions in the bone deposition as indicated by the deposition of lines of arrested growth; (iii) the third stage shows the development of lamellar bone tissue with rest lines in the peripheral part of the cortex suggesting a slowing down of growth prior to death. Most of the skeletal elements are characterized by thick bone walls, extensive secondary reconstruction and the complete infilling of the medullary cavity. However, the radius and a previously studied femur have open medullary cavities with struts of bony trabeculae. Based on histologic structures and comparisons with extant taxa, it is likely that Anteosaurus may have been more terrestrial as its osteology point towards terrestriality, but it may have occasionally inhabited ephemeral pools like modern semi-aquatic Hippopotamus.

Numerical Analysis of Minimum Ground Temperature for Heat Extraction in Horizontal Ground Heat Exchangers

In this work, numerical simulation calculations were performed to investigate the minimum ground temperature that occurs when extracting thermal energy in a horizontal ground heat exchanger system in the Central European climate. The influence of ground thermal conductivity, heat flux extracted from the ground, periodic interruptions in the operation of the heat exchanger, periodic supply of heat energy to the ground, relative humidity of the ambient air, evaporation rate coefficient, and convective heat transfer coefficient on the ground minimum temperature were investigated. Based on the simulation, it was found that the high value of ground thermal conductivity favorably affects the operation of the installation with a ground heat exchanger. Both the reduction of the maximum heat flux taken from the ground, as well as periodic interruptions in the operation of the exchanger effectively protects the ground against excessive cooling. Further, it was found that heat supply to the ground in summer only slightly raises its minimum temperature, as well as the decrease of the relative humidity of the ambient air and evaporation rate coefficient. The change of the convective heat transfer coefficient has no significant impact on the minimum annual ground temperature.

DISCONTINUOUS DRILLING OF INCONEL 718

Inconel 718 as one of the most common nickel-base alloys is mainly characterized by its high-temperature strength. Thus, in particular drilling is subject to high tool wear due to high thermomechanical loads on the cutting edges. To reduce those effects an alternative process design of discontinuous drilling was developed which contains a periodical interruption of the machining process with the aim of a targeted wetting and cooling of the tool at regular intervals. Thus, a significant reduction of the thermal load on the tool should provide a benefit to the drilling process and extend the tool life. Numerical and experimental investigations were used to analyze the introduced process strategy modification.

Аналіз методів фінішного оброблення прецизійних кульок

Аналіз методів фінішного оброблення прецизійних кульок Прикладом елеваторної обробки кульок служить пристрій для доводки кульок, розміщених між двома співвісно розташованими дисками, в нижньому з яких, установленому з можливістю обертання, виконані концентричні канавки. Дане пристосування забезпечує впорядкований рух кульок в робочій зоні і перевід їх з одної доріжки на другу, в результаті чого значно збільшується продуктивність і якість обробки.[1] Був розроблений новий ексцентричний доводочний верстат, власні прототипи авторів. Основна відмінність між цим ексцентриковим доведенням і звичайним концентричним доведенням полягає в тому, що введено зміщення між обертовою віссю і центром кругової V-подібної канавки на нижньому диску-притиру, а верхній диск-притир є плоский і нерухомий. Були проведені експериментальні дослідження з дисками-притирами з м'якої сталі для доведення двох типів куль з нітриду кремнію, отриманих гарячим ізостатичним пресуванням.[2] Спроби вирішити проблему продуктивності привели до створення схем безцентрового шліфування кульок на станках з повздовжньою подачею. На відміно, від відомої схеми обробки циліндричних заготовок провідний круг був виконаний з гвинтовою канавкою несиметричного профілю, а шліфувальний круг оснащений кільцевими канавками. Таке рішення забезпечило обертання кульок від сильного тертя з провідним кругом та додатковим обертанням за рахунок періодичного переривання контакту із шліфувальним кругом. Основна перевага розробленого методу обробки полягає у високій продуктивності процесу. [3] Завдання вирівнювання сітки слідів обробки на поверхні кульок досягається тим, що введені один або більше пружних гальмівників, закріплених на станині верстату з боку відкритих пазів сепаратора так, що завдяки гальмуванню забезпечують додаткове обертання ненавантажених кульок навколо нормалі до площини їхнього руху, що й забезпечує вирівнювання сітки слідів обробки на поверхні кульок завдяки періодичному змінюванню положення миттєвої осі обертання під час руху однією канавкою, що сприяє підвищенню геометричної точності оброблюваних кульок і насамкінець продуктивності обробки невеликих партій кульок.[4] Analysis of finishing methods for precision balls- An example of elevator processing of balls is a device for refining balls placed between two coaxial disks, in the lower of which, installed with the possibility of rotation, made concentric grooves. This device provides an orderly movement of the balls in the working area and their transfer from one track to another, resulting in a significant increase in productivity and quality of processing. [1]- A new eccentric sharpening machine was developed, the authors' own prototypes. The main difference between this eccentric adjustment and conventional concentric adjustment is that an offset is introduced between the rotating axis and the center of the circular V-groove on the lower grinding disc, and the upper grinding disc is flat and stationary. Experimental studies were performed with mild steel grinding wheels to prove two types of silicon nitride balls obtained by hot isostatic pressing. [2]- Attempts to solve the problem of productivity have led to the creation of schemes of centerless grinding of balls on machines with longitudinal feed. In contrast to the known scheme of processing cylindrical workpieces, the guide wheel was made with a helical groove of asymmetrical profile, and the grinding wheel is equipped with annular grooves. This solution provided the rotation of the balls from strong friction with the driving wheel and additional rotation due to the periodic interruption of contact with the grinding wheel. The main advantage of the developed processing method is the high productivity of the process. [3]- The task of leveling the grid of traces of processing on the surface of the balls is achieved by introducing one or more elastic brakes mounted on the frame of the machine from the open grooves of the separator so that by braking provide additional rotation of unloaded balls around normal to the plane of their movement. grids of traces on the surface of the balls due to periodic changes in the position of the instantaneous axis of rotation when moving in one groove, which improves the geometric accuracy of the processed balls and finally the productivity of processing small batches of balls. [4]

Influence of a Discontinuous Process Strategy on Microstructure and Microhardness in Drilling Inconel 718

Nickel-base alloys are proven materials in the fields of the aerospace and oil industry, which is due to their characteristic material properties of high temperature strength, high toughness and good oxidation resistance. These properties are beneficial to applications in technical components in general. However, they also represent challenges for machining. Especially while drilling Inconel 718, high temperatures occur in the chip-formation zone that implicate high thermal load in the material and thus, influence the surface integrity, for example, by causing white layers. Hence, the development of strategies to improve the ability to supply cutting edges with cooling lubricant is becoming increasingly important. In this context, an alternative process design, the discontinuous drilling, takes place, characterized by a periodic interruption of feed motion and thus, chip formation. A minor retraction movement from the contact zone enables the cooling lubricant to reach the cutting edges and to reduce their thermal load. In comparison to the conventional process of drilling Inconel 718, the effects of discontinuous drilling with varying numbers of interruptions on the resulting surface integrity and further parameters of drilling qualities are analyzed. Thereby, the prevention of process-related phase transformations due to thermal impact was discovered when a discontinuous drilling strategy was implemented.

Thermal and flow performance in microchannel heat sink with open-ring pin fins

A unique type of microchannel heat sinks with inline and staggered open-ring pin fins was developed for thermal management of high heat flux devices. The open-ring pin fin was composed of an internal cavity and two inner small and outside large rings with four openings along and perpendicular to the flow direction. Two types of flow channels, i.e., internal separated and merged passages (ISMP) and external convergent-divergent passages (ECDP), were formed. Both experimental and numerical studies were conducted to explore the flow and heat transfer characteristics of both inline and staggered open-ring pin fin microchannels (ORPFM), and their cooling effectiveness was compared with conventional rectangular microchannels. Single-phase convection tests were conducted at Reynolds number of 160–694 using deionized water. The results indicated the inline and staggered ORPFM presented a 56-220% and 77-260% enhancement in Nusselt number compared to conventional rectangular microchannels, respectively. The ORPFM induced periodic flow separations and convergences, successive flow mixing, and periodic interruptions and redevelopment of boundary layers, which contributed to the above heat transfer enhancement. The staggered ORPFM presented a 6-35% larger heat transfer performance, whereas it induced a 9-27% larger pressure drop than the inline one. The staggered ORPFM showed favorable overall thermal-hydraulic performance, and is more favorable for heat dissipation in high heat flux devices.

Augmentation of Fluid Flow and Heat Transfer Characteristics in corrugated Channel: A Review Study

The corrugation configuration played an important role in heat transfer enhancement in many engineering applications such as heat exchangers, microchannel heat sink, solar collectors, etc. The significance of the corrugation configuration is manifested in its ability to offer a larger heat transfer area more than a straight channel. Besides, the periodic interruption and redeveloping of the thermal boundary layer which is an important feature offered by corrugation is remarkably enhanced the heat transfer. The researchers were keen to take advantage of these features and develop them by manipulating geometrical parameters to obtain the optimal results. The current work aims to collect available research data, which focused on improving heat transfer in corrugated channels and identifying the most important factors affecting the performance of corrugated channels. Among the studied shapes of the various operating conditions of the corrugated channels, the researchers unanimously agreed that the trapezoidal shape of the corrugations gives the best thermal improvement with a reasonable pressure drop inside the channels.

Эффективность эзофагопротекции при коротких периодах отмены поддерживающей терапии ингибиторами протонной помпы у пациентов с пищеводом Баррета

Aim. Evaluation of the effectiveness of esophagoprotection in covering up short periods of withdrawal of maintenance therapy with proton pump inhibitors (PPIs) in patients with Barrett's esophagus (BE). Materials and methods. A retrospective analysis of the data of patients with histologically verified BE who received outpatient PPI therapy for at least 12 months was carried out. This cohort was divided into two groups to compare depending on the treatment regimen received. The first group included only patients who take PPIs constantly, while the second group included patients who had periodic interruptions in taking PPIs. In the second group, we analyzed only cases where to cover up the periods of PPI withdrawal the patients used the esophagoprotector Alfasoxx (10 ml 4 times a day, after each meal and at night). In the cohort, demographic data (age, gender), risk factors, length of the BE segment, degree of dysplasia, number of relapses of erosive esophagitis, and the data of high-resolution manometry on movement disorders of the thoracic esophagus (ineffective motility and lack of contractility) were analyzed. Results. The study included 39 patients (28 men and 11 women) with histologically verified BE. The average age was 57,1538 years (95% confidence interval 53.4269–60.8808). The gender structure was dominated by men (n=28). The duration of BE history in the analyzed cohort was 5.6769 years (95% confidence interval, 4.6161–6.7378). The first group consisted of 23 patients who take PPIs constantly. The second group consisted of 16 patients who had periodic interruptions in taking PPIs, which were covered by the esophagoprotector Alfasoxx. In the analyzed cohort, there were no significant differences between the groups in the average length of the BE segment, the number of patients with a long BE segment, the degree of dysplasia, the number of relapses of erosive esophagitis, and the rate of movement disorders of the thoracic esophagus. Conclusion. In routine practice, there are reasons for the temporary withdrawal of PPIs in patients with BE, which requires the administration of course esophagoprotection to cover up the risks. The results of this retrospective comparative study demonstrate the effectiveness of this strategy.

Structural and dynamic properties of short-period GaN/AlN superlattices grown by submonolayer digital epitaxy

Structural and dynamic properties of short-period GaN/AlN superlattices with the thicknesses of the constituent layers varying from two to several monolayers, grown using the method of submonolayer digital molecular beam epitaxy, are experimentally and theoretically studied. It is established that in the grown samples there are two types of periodicity. One type is formed by periodic sequence of GaN and AlN layers in the superlattice, and the second one is related with periodic interruptions in the growth of superlattice for the evaporation of excess Ga metal. The dependences of the positions and intensities of the lines in the Raman spectra on the period of the superlattice are determined, and microscopic nature of optical phonon modes is established. The doublet structure of the E(TO) lines localized in the GaN and AlN layers of superlattice, genetically related to the E 2(high) and E1 phonon branches of the bulk crystal, is first discovered and explained. A strong dependence of the polar modes localized in the AlN layer on the thickness of layer forming the superlattice is revealed. The results of complex studies will improve the accuracy of quantitative estimation of important parameters of superlattice structures and can be used to optimize growth parameters for the fabrication of structurally perfect short-period GaN/AlN superlattices.

Numerical analysis of the flow and heat transfer characteristics in serpentine microchannel with variable bend amplitude

PurposeThis study aims to propose the increase of heat dissipation requirements of modern electronic equipment and the fast development of micro-scale manufacturing technologies. The heat transfer mechanism is studied in-depth, especially for its pattern of secondary flow caused by the repeated inversion of centrifugal force. Effects of η on the frictional pressure drop and average Nusselt number are studied and the performance of such microchannel heat sink with various bend amplitudes is comprehensively evaluated. These results can provide important insight into the optimal design of this novel design configuration for microelectronics cooling.Design/methodology/approachA three-dimensional model based on the finite volume approach and SIMPLEC algorithm is performed to test an innovative serpentine microchannel, which behaves differently from conventional serpentine microchannel due to the significant effect of centrifugal force inversion.FindingsThe effect of centrifugal force significantly influences the flow and thermal fields which are responsible for the enhancement in heat transfer coefficient. The number, size and intensity of vortices increase with increasing Re, and the vortices are reformed at every change of the geometry in a periodic fashion. The serpentine microchannel studies more effectively at larger bend amplitude. Pressure fluctuations and temperature variation are greater with increasing bend amplitude.Practical implicationsSeveral techniques have been developed to augment single-phase convective heat transfer in channels. One technique is to use a serpentine channel that enhances the heat transfer due to flow mixing and periodic interruption of thermal boundary layers. This technique has been applied to micro-heat exchangers, thermal regenerators and mini/microreactors.Social implicationsThe optimal design of this novel design configuration for microelectronics cooling can be attained. It will become an effective cooling technology for solving the increasing of heat dissipation requirements of modern electronic equipment.Originality/valueThe flow and heat transfer characteristics are first presented for the circular serpentine microchannel made up of alternate U-bends without interposed straight segments. The present study first examines the effect of such centrifugal force inversion on velocity contour, pressure distribution and temperature distribution. The patterns of secondary flow along the flow passage caused by the repeated inversion of centrifugal force are further studied in depth. The effect of bend amplitude on the flow and heat transfer is explored and the performance of such microchannel heat sink has been comprehensively evaluated.

High-Throughput Growth of Wafer-Scale Monolayer Transition Metal Dichalcogenide via Vertical Ostwald Ripening.

For practical device applications, monolayer transition metal dichalcogenide (TMD) films must meet key industry needs for batch processing, including the high-throughput, large-scale production of high-quality, spatially uniform materials, and reliable integration into devices. Here, high-throughput growth, completed in 12 min, of 6-inch wafer-scale monolayer MoS2 and WS2 is reported, which is directly compatible with scalable batch processing and device integration. Specifically, a pulsed metal-organic chemical vapor deposition process is developed, where periodic interruption of the precursor supply drives vertical Ostwald ripening, which prevents secondary nucleation despite high precursor concentrations. The as-grown TMD films show excellent spatial homogeneity and well-stitched grain boundaries, enabling facile transfer to various target substrates without degradation. Using these films, batch fabrication of high-performance field-effect transistor (FET) arrays in wafer-scale is demonstrated, and the FETs show remarkable uniformity. The high-throughput production and wafer-scale automatable transfer will facilitate the integration of TMDs into Si-complementary metal-oxide-semiconductor platforms.

Mechanically Assisted Bioluminescence with Natural Luciferase.

Mechanochemical analogues have recently been established for several enzymatic reactions, but they require periodic interruption of the reaction for sampling, dissolution, and (bio)chemical analysis to monitor their progress. By applying a mechanochemical procedure to induce bioluminescence analogous to that used by the marine ostracod Cypridina (Vargula) hilgendorfii, here we demonstrate that the light emitted by a bioluminescent reaction can be used to directly monitor the progress of a mechanoenzymatic reaction without sampling. Mechanical treatment of Cypridina luciferase with luciferin generates bright blue light which can be readily detected and analyzed spectroscopically. This mechanically assisted bioluminescence proceeds through a mechanism identical to that of bioluminescence in solution, but has higher activation energy due to being diffusion-controlled in the viscous matrix. The results suggest that luciferases could be used as light-emissive reporters of mechanoenzymatic reactions.

Mechanically Assisted Bioluminescence with Natural Luciferase

AbstractMechanochemical analogues have recently been established for several enzymatic reactions, but they require periodic interruption of the reaction for sampling, dissolution, and (bio)chemical analysis to monitor their progress. By applying a mechanochemical procedure to induce bioluminescence analogous to that used by the marine ostracod Cypridina (Vargula) hilgendorfii, here we demonstrate that the light emitted by a bioluminescent reaction can be used to directly monitor the progress of a mechanoenzymatic reaction without sampling. Mechanical treatment of Cypridina luciferase with luciferin generates bright blue light which can be readily detected and analyzed spectroscopically. This mechanically assisted bioluminescence proceeds through a mechanism identical to that of bioluminescence in solution, but has higher activation energy due to being diffusion‐controlled in the viscous matrix. The results suggest that luciferases could be used as light‐emissive reporters of mechanoenzymatic reactions.

Defoliation frequency affects litter responses and nitrogen excretion by heifers in palisadegrass–forage peanut pastures

AbstractLegumes can contribute significantly to nitrogen (N) input in grazing systems. Grazing management is a critical factor affecting N cycling in mixed pastures, altering the legume N input as a result. This study assessed how defoliation frequency affects N cycling in rotationally stocked palisadegrass (Brachiaria brizantha) and forage peanut (Arachis pintoi) pastures. Treatments included four grazing management strategies, defined by the rest period interruption when the canopy reached 90 (90LI), 95 (95LI), and 100% (100LI) of photosynthetically active radiation interception (LI), and a fixed rest period of 42 d (42D). A 2‐yr experimental period was adopted. Existing litter was greater at 100LI (2208 vs. 1964 kg ha−1; average of 42D, 90LI, and 95LI, respectively). Greater defoliation frequency (42D and 90LI) resulted in increase of litter legume proportion, resulting in greater decomposition rate, lower litter half‐life (p < .001, and p = .015, respectively), and greater N cycling (91 vs. 64 kg ha−1 season−1). Less frequent defoliation (100LI) resulted in reduced total forage intake, proportion of legume intake, and lower N intake compared with other treatments (p = .007, p = .081, and p < .001, respectively). Greater defoliation frequency increased N cycling via litter, but did not affect excretion due to compensation with stocking rate. Defoliation frequency between 90 and 95% LI optimizes N cycling in palisadegrass‐forage peanut mixed pastures.

A study of turbulent heat transfer in convergent-divergent shaped microchannel with ribs and cavities using CFD

This paper presents the effects of microchannel shape with ribs and cavities on turbulent heat transfer. Three-dimensional conjugate heat transfer using the SST k-ω turbulence model has been investigated for four different microchannels, namely, rectangular, rectangular with ribs and cavities, convergent-divergent (CD) and convergent-divergent with Ribs and Cavities (CD-RC). The flow field, pressure and temperature distributions and friction factor are analyzed, and thermal resistance and average Nusselt number are compared. The thermal performance of the CD-RC microchannel is found to be better than that of other microchannels considered in terms of an average Nusselt number increased from 16% to 40%. Heat transfer increases due to a strong fluid mixing and periodic interruption of boundary-layer. It is observed that with an increase in Reynolds number (Re), the thermal resitance drops rapidly. The thermal resistance of the CD-RC microchannel is decreased by 30% than that of the rectangular microchannel for Re ranging from 2500 to 7000. However, such design of microchannel loses its heat transfer effectiveness due to a high pumping power at high values of Re.

Physical and physiological quality of intermittent soybean seeds drying in the spouted bed

The aim of this study was to perform the physical and physiological quality analysis of intermittent soybean seeds drying in the spouted bed. Mechanical damages and physiological properties were evaluated by tests of germination, first germination count, seedling length, tetrazolium, sodium hypochlorite, and X-ray. Five different intermittency profiles and two different intermittency methodologies with periodic reduction and interruption of the air flow were employed. Continuous and intermittent processes with shorter periods of reduced air flow (A.1) provided a lower degree of seed deterioration, considering both physiological and physical aspects. The findings of this study contributed to identify the distinct trend of intermittency application in the spouted bed in relation to other dryers when seed quality attributes are demanded, highlighting as a promising field for further studies.

Metalorganic Vapor Phase Epitaxy of Thick and Uniform Single Crystal CdTe Epitaxial Layers on (211) Si Substrates for X-ray Imaging Detector Development

Metalorganic vapor phase epitaxy of uniform and thick single crystal CdTe on (211) Si substrates has been studied for x-ray imaging detector development. Periodic growth interruptions are introduced during thick CdTe layer growth in order to improve crystal quality. Thick single crystal CdTe layers with uniform material properties were obtained. When compared to continuously grown crystals, these growth interrupted crystals exhibited better uniformity in thickness and x-ray rocking curve values throughout the wafer. We further developed a (20 × 20) pixels x-ray imaging array using these crystals. The detector showed a low dark current per pixel, and the value was uniform among the pixels which are required criteria to improve the uniformity of detector response. These results demonstrate single crystals CdTe obtained in this study are suitable for x-ray imaging detector development.

Heat transfer and pressure drop of a periodic expanded-constrained microchannels heat sink

Thermal management of high heat flux devices in many areas has promoted the development of advanced microchannel heat sinks. This study proposed a novel type of periodic expanded-constrained microchannels (PECM) heat sink with flow separation and convergence passages. Its convective heat transfer and pressure drop performance was explored by both experimental tests and numerical simulations, and its cooling efficiency was compared with rectangular microchannels. Forced convection tests were conducted at Reynolds number of 150–820 and two levels of heat fluxes using deionized water. Results indicated that the PECM samples showed significant heat transfer enhancement, i.e., 50% to 117%, compared to the rectangular counterpart in the test ranges. Such enhancement can be attributed to that the periodic expanded-constrained configurations of PECM induced periodic interruption and redevelopment of thermal and hydraulic boundary layers, as well as good flow separation, fluid acceleration and mixing. Moreover, the heat transfer enhancement of PECM was not accompanied with the expense of pressure drop penalty, and all the PECM samples reduced the pressure drop for 10–74% compared to the rectangular counterpart. Besides, the effect of microchannel gap width in the main flow passages on the thermal and hydraulic performance was also assessed by preparing three samples with microchannel gap widths of 0.5, 0.8 and 1.0 mm. It was found that the pressure drop and thermal resistance of PECM increased monotonically with decreasing the microchannel gap widths. The sample with the largest microchannel gap width of 1.0 mm presented the best overall thermal and hydraulic performance.

3D Cartesian fast interrupted steady-state (FISS) imaging.

PurposeTo enable intrinsic and efficient fat suppression in 3D Cartesian fast interrupted steady‐state (FISS) acquisitions.MethodsA periodic interruption of the balanced steady‐state free precession (bSSFP) readout train (FISS) has been previously proposed for 2D radial imaging. FISS modulates the bSSFP frequency response pattern in terms of shape, width and location of stop band (attenuated transverse magnetization). Depending on the FISS interruption rate, the stop band characteristic can be exploited to suppress the fat spectrum at 3.5 ppm, thus yielding intrinsic fat suppression. For conventional 2D Cartesian sampling, ghosting/aliasing artifacts along phase‐encoding direction have been reported. In this work, we propose to extend FISS to 3D Cartesian imaging and report countermeasures for the previously observed ghosting/aliasing artifacts. Key parameters (dummy prepulses, spatial resolution, and interruption rate) are investigated to optimize fat suppression and image quality. FISS behavior is examined using extended phase graph simulations to recommend parametrizations which are validated in phantom and in vivo measurements on a 1.5T MRI scanner for 3 applications: upper thigh angiography, abdominal imaging, and free‐running 5D CINE.ResultsUsing optimized parameters, 3D Cartesian FISS provides homogeneous and consistent fat suppression for all 3 applications. In upper thigh angiography, vessel structures can be recovered in FISS that are obscured in bSSFP. Fat suppression in free‐running cardiac CINE resulted in less fat‐related motion aliasing and yielded better image quality.Conclusion3D Cartesian FISS is feasible and offers homogeneous intrinsic fat suppression for selected imaging parameters without the need for dedicated preparation pulses, making it a promising candidate for free‐running fat‐suppressed imaging.