Thin Backing Research Articles

Impedance characterization of substrate leakage in wafer bonded CMUTs

This work investigates substrate leakage in Capacitive Micromachined Ultrasonic Transducers, (CMUTs) having thin backings. CMUTs produced with solid or rigid substrates have a high Q resonance with flat baseline. However, if the operating wavelength of CMUT becomes larger than the thickness of substrate the real part of cell impedance shows elevated baselines with more leakage at DC than at higher frequencies. When a clamped CMUT membrane is excited harmonically the vibrations produced are counterbalanced by the backing medium. Hence some of the energy is coupled to substrate as loss resulting in a lower mechanical Q of resonance. We first derive this energy coupled to the backing medium using FEA analysis considering the velocity field and associated tensile stresses in a thin backing. Substrate impedance is found numerically from isotropic damping of dispersive elastic waves in the backing. This backing impedance is introduced as a shunt mechanical loss across the transduction force in equivalent circuit model. We characterize the measured impedance of CMUT cells with both FEMs and linear circuit models. Simulations results closely agree with the measured impedance levels, frequency and bandwidth of resonance.

Ballistic performance of composite armor impacted by 7.62 mm armor projectile

The purpose of this study is to investigate the effectiveness of composite armor against 7.62 mm ballistic threats. A sandwich panel construction consisting of a 96% alumina ceramic strike face, an annealed aluminum alloy 7075 cubic lattice sandwich panel, and a thin aluminum backing plate were used to create hard armor. The ballistic test based on NIJ standard level III was performed using 7.62 mm × 51 mm NATO projectiles at an impact velocity of 847 ± 9.1 m∙s-1. The influences of the alumina strike face panel with thicknesses of 7, 10, and 14 mm on the ballistic performance were investigated. The results of the ballistic test suggest that hard armor designs can resist a ballistic impact of 7.62 mm × 51 mm NATO projectiles without penetrating them. With the increase in thickness of alumina ceramic tile, the deformation of the aluminum backing plate decreased. Furthermore, the annealed aluminum alloy 7075 cubic lattice sandwich panel could be able to absorb the residual kinetic energy of the projectile after it was eroded by the ceramic strike panel. The damaged targets after ballistic impact were presented. Collectively, these results indicate that the armor composites in this study may be used in military vehicle applications.

Electrospraying deposition and characterization of potassium chloride targets for nuclear science measurements

Natural and isotopically enriched KCl targets were prepared using specially formulated KCl solutions, deposited by electrospraying on thin (1.5μm) gold backings, followed by a short annealing in a preheated (350–450 °C) furnace. Various techniques, such as X-ray fluorescence (XRF), scanning electron microscopy (SEM) imaging, and energy-dispersive X-ray spectroscopy (EDS), were used to characterize the produced targets. A white neutron beam at the Los Alamos Neutron Science Center (LANSCE) facility was also used to verify the estimated atomic percentages of the enriched 40KCl targets. KCl was deposited relatively uniformly as large particles rather than films on the gold surface. This method can be broadly extended to make stable targets that are difficult to produce with other methods and more exotic radioactive targets required for research in fundamental sciences and applications.

Reciprocating Arc Silicon Strain Gauges.

Currently, silicon-strain-gauge-based diaphragm pressure sensors use four single-gauge chips for high-output sensitivity. However, the four-single-gauge configuration increases the number of glass frit bonds and the number of aluminum wire bonds, reducing the long-term stability, reliability, and yield of the diaphragm pressure sensor. In this study, a new design of general-purpose silicon strain gauges was developed to improve the sensor output voltage while reducing the number of bonds. The new gauges consist grid patterns with a reciprocating arc of silicon piezoresistors on a thin glass backing. The gauges make handling easier in the bonding process due to the use of thin glass for the gauge backing. The pressure sensors were tested under pressure ranging from 0 to 50 bar at five different temperatures, with a linear output with a typical sensitivity of approximately 16 mV/V/bar and an offset shift of -6 mV to 2 mV. The new approach also opens the possibility to extend arc strain gauges to half-bridge and full-bridge configurations to further reduce the number of glass frit and Al wire bonds in the diaphragm pressure sensor.

Low Trapping Effects and High Electron Confinement in Short AlN/GaN-On-SiC HEMTs by Means of a Thin AlGaN Back Barrier

In this paper, we report on an enhancement of mm-wave power performances with a vertically scaled AlN/GaN heterostructure. An AlGaN back barrier is introduced underneath a non-intentionally doped GaN channel layer, enabling the prevention of punch-through effects and related drain leakage current under a high electric field while using a moderate carbon concentration into the buffer. By carefully tuning the Al concentration into the back barrier layer, the optimized heterostructure offers a unique combination of electron confinement and low trapping effects up to high drain bias for a gate length as short as 100 nm. Consequently, pulsed (CW) Load-Pull measurements at 40 GHz revealed outstanding performances with a record power-added efficiency of 70% (66%) under high output power density at VDS = 20 V. These results demonstrate the interest of this approach for future millimeter-wave applications.

Laser-printed emissive metasurface as an optical security platform

Optical security is a promising application of metasurfaces because light has large degrees of freedom in metasurfaces. Although many different structures/materials have been proposed for this purpose, the fabrication of dynamic metasurfaces in a straightforward and scalable manner while maintaining a high security level remains a significant challenge. Herein, a metasurface consisting of a phase-changing Ge2Sb2Te5 (GST) layer and a thin metal back reflector is presented to space-selectively and dynamically control the infrared emission of the surface by a spatially modulated pulsed laser beam. Unlike conventional laser processes using a focused beam, the employed laser printing is an expanded beam-based parallel process that enables the fabrication of wafer-sized emission patterns. Owing to the multispectral responses of GST, mutually independent visible and infrared images can be printed in one region. Grayscale emission patterns can also be obtained by gradually modulating the spatial profile of the laser beam, which makes the replication of laser-printed emission patterns extremely difficult. We also demonstrate that colors images can be obtained by depositing IR lossless layer on the GST surface. All these features indicate that the presented emissive metasurface has the potential for use as an effective platform for anti-counterfeiting.

Development of 187Re targets for heavy ion induced reactions

To perform nuclear reaction experiment, very good quality, uniform and thin targets are necessary. In order to carry out evaporation residue cross section measurement of 19F+187Re reaction using Hybrid Recoil mass Analyzer (HYRA) facility at Inter - University Accelerator Center (IUAC) 187Re targets of thickness 200 μg/cm2 are required. More than 20 targets of 187Re of 200 μg/cm2 thickness with thin carbon backing have been prepared using 70 mg of 187Re. Being one of the highest melting points of all elements, high temperature involved in the process and limited amount of available isotopic material are the major constraints during the target development of 187Re. The targets have been successfully used for the nuclear reaction experiment. The method used for the development of several 187Re targets with minimum material consumption and the detailed characterization techniques applied for studying the targets are discussed in detail.

A Thin Transducer With Integrated Acoustic Metamaterial for Cardiac CT Imaging and Gating.

Coronary artery disease (CAD) is a leading cause of death globally. Computed tomography coronary angiography (CTCA) is a noninvasive imaging procedure for diagnosis of CAD. However, CTCA requires cardiac gating to ensure that diagnostic-quality images are acquired in all patients. Gating reliability could be improved by utilizing ultrasound (US) to provide a direct measurement of cardiac motion; however, commercially available US transducers are not computed tomography (CT) compatible. To address this challenge, a CT-compatible 2.5-MHz cardiac phased array transducer is developed via modeling, and then, an initial prototype is fabricated and evaluated for acoustic and radiographic performance. This 92-element piezoelectric array transducer is designed with a thin acoustic backing (6.5 mm) to reduce the volume of the radiopaque acoustic backing that typically causes arrays to be incompatible with CT imaging. This thin acoustic backing contains two rows of air-filled, triangular prism-shaped voids that operate as an acoustic diode. The developed transducer has a bandwidth of 50% and a single-element SNR of 9.9 dB compared to 46% and 14.7 dB for a reference array without an acoustic diode. In addition, the acoustic diode reduces the time-averaged reflected acoustic intensity from the back wall of the acoustic backing by 69% compared to an acoustic backing of the same composition and thickness without the acoustic diode. The feasibility of real-time echocardiography using this array is demonstrated in vivo, including the ability to image the position of the interventricular septum, which has been demonstrated to effectively predict cardiac motion for prospective, low radiation CTCA gating.

Laser-printed emissive metasurface implemented with a planar thin-film resonator

Optical security is a promising application of metasurfaces because light has large degrees of freedom in metasurfaces. Although many different structures/materials have been proposed for this purpose, the fabrication of dynamic metasurfaces in a straightforward and scalable manner while maintaining a high security level remains a significant challenge. Herein, a metasurface consisting of a phase-changing Ge2Sb2Te5 (GST) layer and a thin metal back reflector is presented to space-selectively and dynamically control the infrared emission of the surface by a spatially modulated pulsed laser beam. Unlike conventional laser processes using a focused beam, the employed laser printing is an expanded beam-based parallel process that enables the fabrication of wafer-sized emission patterns. Owing to the multispectral responses of GST, mutually independent visible and infrared images can be printed in one region. Grayscale emission patterns can also be obtained by gradually modulating the spatial profile of the laser beam, which makes the replication of laser-printed emission patterns extremely difficult. These encouraging features are experimentally verified using rigid and flexible substrates, indicating that the presented emissive metasurface has the potential for use as an effective platform for anti-counterfeiting.

Performance of Composite Metal Foam Armors against Various Threat Sizes

The ballistic capabilities of composite metal foam (CMF) armors were experimentally tested against a 14.5 × 114 mm B32 armor-piercing incendiary (API) and compared to various sizes of armor-piercing (AP) ballistic threats, ranging from a 7.62 to 12.7 mm. Three different arrangements of layered hard armors were designed and manufactured using ceramic faceplates (in one layer, two layers or multiple tiles), a combination of ceramic and steel face sheets, with a single-layered CMF core, and a thin aluminum backing. The performance of various CMF armor designs against the 14.5 mm rounds are compared to each other and to the performance of the rolled homogeneous armor standard to identify the most efficient design for further investigations. The percentage of kinetic energy absorbed by the CMF layer in various armor arrangements and in tests against various threat sizes was calculated and compared. It appears that the larger the threat size, the more efficient the CMF layer will be due to a greater number of hollow metal spheres that are engaged in absorbing the impact energy. The results from this study will help to model and predict the performance of CMF armors against various threat sizes and impact energies.

Structural response of monolithic and multi-layered circular metallic plates under repeated uniformly distributed impulsive loading: An experimental study

A series of 112 experiments were conducted to investigate the response of monolithic and multi-layered metallic plates under repeated uniform impulsive loading up to five times. 15 various testing groups were considered to study the effects of different charge masses, layering configurations, layering arrangements, layer thicknesses, and stand-off distances on the central deflection of single-, double-, triple-layered and triple-layered mixed plates made of aluminum alloy and mild steel materials. The results showed that the triple-layered mixed configuration made of thick aluminum middle and front plates and thin mild steel plate has the best performance compared to other tested configurations from the 1st to 5th loading cycle while the triple-layered steel plate has the poorest performance at the 1st and 2nd loading cycle. Also, the triple-layered mixed configuration with thin mild steel back and front layers showed the poorest blast performance after the 2nd cycle. Additionally, empirical design formulae were proposed to predict the central deflection of monolithic and multi-layered plates under repeated impulsive loading based on new dimensionless numbers.

Pilot-study switchable film dressing & elderly skin/patients with chronic wounds: A non-interventional, non-placebo-controlled, national pilot study

Abstract Aim Film dressings were one of the first modern wound-dressing products. During the removal of the dressing skin stress occurs. An essential role is shearing force between skin and wound dressing playing [3]. This problem includes missing elasticity, flexibility and too strong adhesion [3,4]. The present study was initiated to evaluate if the switchable formulation of the adhesive ensures a durable and strong enough adhesion. Illumination of the film dressing with the UV-A lamp irreversibly switches the adhesion from strong to weak and guarantees a painless/comfortable removal of the dressing. Methods The present study evaluated suitability for use as well as user and patient satisfaction during use of the tested film on patients with chronic wounds. The used film dressing consists of a thin film backing with a non‑latex adhesive. Before removal the adhesion is reduced by illuminating the dressing with the UV-A lamp. Results 54 patients were included in the study. At each dressing change, pain level after dressing change was rated lower compared to the pain level before dressing change. Overall, pain level decreased over the study period. Reactions on the wound edge/wound surroundings have not been reported. Discussion The clinicians gave favourable scores for the tested film dressing. The overall satisfaction with the product was rated very good. Tolerability such as pain during wearing the dressing and upon removal were given good scores. Skin irritation caused in the use of the film dressing did not occur. Conclusion The switchable function of the adhesive allows the adhesion of the film dressing to the skin to be reduced when illuminated by the supplied UV-A lamp. The results of the present study show that the reduced adhesion upon illumination enables easy and comfortable removal of the dressing.

Mitigation of shock loading on structures using aqueous methylcellulose solution

Shock mitigation performance of aqueous methylcellulose hydrogel and water for structural applications was investigated through two dynamic loading instruments: Instrumented bar and shock tube. While aqueous methylcellulose solutions have previously been found to attenuate impact-induced forces passing through them by a unique liquid-to-solid phase transition, this is the first time studied as shock mitigators to structural elements. The results obtained with aqueous methylcellulose as mitigator were compared with an equivalent experiment conducted with water as damping medium. The liquid was loaded into a specially designed hollow aluminum box, built to allow transmission of dynamic stress waves to a thin back plate. Determination of the liquid's attenuation performance was based on the 3D Digital Image Correlation technique with high-speed photography to obtain the full-field real-time deformation data of the back-face plate throughout the dynamic loading event. It was found that upon high rate loading with the instrumented bar, the aqueous methylcellulose solution decreases the maximum out of plane displacement resulting from the dynamic loading by as much as 40% compared to water, and significantly damps the structural vibrations of the back-face plate. On the other hand, upon relatively low rate loading with shock tubes, water and aqueous methylcellulose solutions provide the same magnitude of out of plane displacement, however, the damping ratio (Logarithmic Decrement) of the structure through aqueous methylcellulose solutions is 45% greater than through water. The findings are analyzed and rationalized in terms of imparted mechanical power.

Pilot-Study Lumina Switchable Post-Op Dressing & Postsurgical Wounds: A Non-interventional, Non-placebo-controlled, National Pilot Study

Dressings applied to primarily closed surgical incisions should be appropriate interactive dressing [13] and demonstrate an ability to protect the wound from contaminants and trauma, manage exudate, and avoid excessive pressure to the incision line. Additionally, they should be flexible, well fixed to the skin on application, skin protective (e.g. reduce the risk of blistering or irritation, not excessively adhesive) and waterproof [14]. Film dressings were one of the first modern wound-dressing products. They are extremely flexible, transparent and adhesive. During the removal of the dressing skin stress occurs. An essential role are shearing and friction forces between skin and wound dressing playing. This problem includes missing elasticity, flexibility and too strong adhesion. A non-interventional, non-placebo-controlled, national pilot study was done to prove a new shearing force reducing technique and dressing. The used post-op dressing consists of a thin film backing with a switchable polyurethane adhesive and non-adhering absorption pad. Before removal the adhesion is reduced by illuminating the dressing with the UV-A lamp. 52 patients at a mean age of 55.79 years (SD±16.22) with a total of 52 wounds were included in the study, all of them finalized the 1-week study period. At baseline, pain was measured with a mean of 3.52 (SD±1.26), during the study period pain decreased to a mean of 2.10 (SD±0.97) (VAS 0=no pain, 10=excruciating pain). Significance was calculated as 0,000 (paired t-test). At each dressing change, pain level after dressing change was rated lower compared to the pain level before dressing change. Overall, pain level decreased over the study period. The removal of the dressing after illumination with the UV-A lamp was rated in mean with 1.79 (2. Visit) and 1.86 (3. Visit) on the 6–point-scale (1=very good – 6=insufficient). Significance was calculated as 0,000 for visit 3 (one sample t-test [test value=3,0]). Reactions on the wound edge/wound surroundings have not been reported. In contrast, a reduction of maceration and redness of the wound edge/wound surrounding was observed. The results confirm that the adhesive ensures a safe and effective occlusion/fixation of the dressing and that the strong adhesion enables dressing to function according to specification. There was no deterioration of the wound situation or an infection in any of the cases. The switchable function of the adhesive allows the adhesion of the post-op dressing to the skin to be reduced when illuminated by the supplied UV-A lamp. The results of the present study show that the reduced adhesion upon illumination enables easy and comfortable removal of the dressing.

Measurement of the 242Pu(n, γ) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combining different neutron beams and techniques. The thermal point was determined at the Budapest Research Reactor by means of Neutron Activation Analysis and Prompt Gamma Analysis, and the resolved (1 eV - 4 keV) and unresolved (1 - 500 keV) resonance regions were measured using a set of four Total Energy detectors at the CERN n_TOF-EAR1.

240Pu target preparation on thin backing foils for GRETINA experiments using ATLAS

Recent measurements of the octupole strength to the highest spin states in 240Pu were performed using sub-barrier Coulomb excitation in order to unambiguously and convincingly demonstrate the existence of the rotational-aligned phonon condensation in this nucleus. The 240Pu targets were prepared at the Center for Accelerator Target Science by molecular plating onto thin backing foils of C and Al. The required plutonium oxide dissolution, molecular plating methodology, plating results, and in-beam target performance will be discussed.

Pilot-study switchable film dressing & NPWT: A non-interventional, non-placebo-controlled, national pilot study

Abstract Aim Negative pressure wound therapy (NPWT) has become an accepted treatment modality for acute and chronic wounds with accelerated healing rates observed. To prevent air from being sucked in from the external environment, the wound and the filler that rests inside or upon the wound are hermetically sealed with an airtight adhesive polyurethane drape that is permeable to water vapour, transparent, and bacteria proof [ 1 ]. During the removal of the dressing skin stress occurs. An essential role is shearing force between skin and wound dressing playing [ 7 ]. This problem includes missing elasticity, flexibility and to strong adhesion [ 7 , 8 ]. The present study was initiated to evaluate if the switchable formulation of the adhesive ensures a durable and effective occlusion of the dressing and function of the NPWT, but also that the defined adhesion is in the range of patient- and user satisfaction. Methods The used film dressing consists of a thin film backing with a non‑latex adhesive. Before removal the adhesion is reduced by illuminating the dressing with the UV-A lamp. Results 50 patients at a mean age of 71.7 years (SD ± 12.0) with a total of 51 wounds (one patient had two wounds) were included in the study. Wound bed condition (multiple answers possible) was rated as granulation (47), sloughy (33) and necrotic tissue (3). Wound bed condition had improved during the short course of the study with a reduction of sloughy and necrotic tissue. Wound pain/adjacent to the wound pain was specified with a mean of 3,44 (SD ± 1,4) on the VAS (0 = no pain, 10 = excruciating pain) and was decreasing to a mean of 2,3 (SD ± 1,2) at the final visit (see Table 2 and Fig. 2 ). The application of the dressing/occlusion with the dressing was rated in mean with 1,02 (1. Visit) and 1,00 (2. Visit) on the 6–point-scale (1 = very good – 6 = insufficient). Significance was calculated as 0,000 for visit 1 (one sample t-test [test value=3,0]). Reactions on the wound edge/wound surroundings have not been reported. In contrast, a reduction of maceration, redness and dryness of the wound edge/wound surrounding was observed (see Table 1 ). Discussion The clinicians gave favourable scores for the tested film dressing regarding application of the dressing, application of NPWT/connection with the suction, overall satisfaction with the application, tightness of the dressing since the last dressing change, easiness of illuminating the dressing with the UV-A lamp and removal of the dressing after illumination with the UV-A lamp. The overall satisfaction with the product was rated very good. Tolerability such as pain during wearing the dressing and upon removal were given good scores. Existing wound edge and wound surroundings findings like maceration, redness etc. at visit 1 decreased. Skin irritation caused in the use of the film dressing did not occur. Conclusion The results confirm that the adhesive ensures a safe and effective occlusion of the dressing and that the strong adhesion enables the NPWT to function according to specification. The switchable function of the adhesive allows the adhesion of the film dressing to the skin to be reduced when illuminated by the supplied UV-A lamp. The results of the present study show that the reduced adhesion upon illumination enables easy and comfortable removal of the dressing.

Ballistic performance of composite metal foam against large caliber threats

The goal of this study is to investigate the effectiveness of Composite Metal Foam (CMF) armors against 0.50 caliber ballistic threats. A hard armor was manufactured using a sandwich panel construction consisting of a ceramic faceplate, a CMF core, and a thin aluminum back plate. The hard armor system was tested against 0.50 caliber (12.7 × 99 mm) ball and armor piercing (AP) rounds. The CMF armors were tested with a variety of areal densities at impact velocities between 500 and 885 m/s. The armors stopped the threats at speeds up to 819 m/s without penetration. The CMF layer was found to absorb 73–76% and 69–79% of the kinetic energy of the ball and AP round respectively. When compared to rolled homogeneous steel armor (RHA), the CMF hard armors, in their current unoptimized condition, have a mass efficiency ratio of approximately 2.1. The CMF armor offers a much needed weight savings without sacrificing protection. Finite element analysis was completed using ANSYS/AUTODYN Explicit Dynamics solver to study the material interactions and impact. The results are shown to be in good agreement with the experimental findings.

Evaluation of the body condition score of draft horses of the city of Imperatriz, State of Maranhão

The objective of this study was to analyze the mean values, standard deviation, minimum and maximum values of the weight and parameters of the body conditions score between males and females of the traction horses in the municipality of Imperatriz, State of MA. The animals were attended by the Healthy Horse Horse Program that had as objective to improve the equine welfare and consequently the socioeconomic profile of the cartwrights who have as income source these animals. A total of 146 animals were attended, weekly weighing and visualization of the scores (extremely thin, very thin, thin, moderately thin, moderate, moderately fleshy, fleshy, fat and obese). The statistical results revealed a mean weight for males of 283.08 and 289.33 for females, with a mean height of 142.37 and 139.31 and Pearson's correlation (0.452**), the R2 regression analysis recorded values of F = 33.12 **. The body score revealed for neck, garrote, shoulder, ribs, back and back of the males classification lean (3), females registered for neck, very thin (2), garrote, shoulder, costa, rib and lean back (3). Pearson's correlation recorded values highly significant for weight and height (0.452**), height with neck (0.234**), club (0276**), shoulder (0.348**) and ribs (0.253**). Neck with garrote (0.511**), shoulder (0.458**), rib (0.363**), coast (0.377**), back (0.330**), shoulder garment values (0.484**), rib 0.364**), back (0.429**), back (0.322**). Based on the data analyzed it is concluded that the average live weight of the horses examined being below the average required for the service provided by them, to mean height showed values ranging from 142.37 cm for males and 139.31 cm for females. The indices of body conditions of the animals examined are below the required range of 3 to 4.

Three dimensional fatigue damage evolution in non-crimp glass fibre fabric based composites used for wind turbine blades

This work studies the tension fatigue damage progression of a uni-directional glass fibre composite made from a non-crimp fabric similar to those used for the main load carrying parts of a wind turbine blade. The spatial damage progression in a chosen region of a test specimen is monitored on a micro-structural scale by ex-situ X-ray computed tomography. The centimetre sized specimen remains uncut during the ex-situ experiment. The experimental results indicate that uni-directional fibre fractures initiate from matrix cracks related to the structure of the fabric: first in the thin off-axis backing bundles at triple cross-over regions where the ±45∘ and 90∘ backing bundles intersect each other and lie close to a uni-directional bundle, and later followed by damage initiation in the other cross-over regions. Uni-directional fibre fractures were seen to increase in number with increasing number of cycles, and mainly progress in the thickness direction of uni-directional bundles (away from the backing bundles). Furthermore, the crack face separation of individual broken uni-directional fibres was observed to gradually increase with an increasing number of cycles. The progression path of the uni-directional fibre fractures was seen to be very dependent on the local backing bundle arrangement.