Indirect Measurement Method Research Articles

Comprehending the underlying mechanism behind directly/indirectly obtained large electrocaloric response in Bi0.5Na0.5TiO3-based relaxor ferroelectrics

Lead-free ferroelectric electrocaloric (EC) materials are promising candidates for the next generation of cooling materials. Bi0.5Na0.5TiO3 (BNT)-based relaxor ferroelectrics, one of the most representative EC materials, exhibit a superior electrocaloric effect (ECE) near the depolarization temperature (Td). However, there are more and more concerns over the reliability of the widely used indirect measurement method. Here, to comprehend the difference between indirectly and directly obtained ECE results in BNT-based system, the applicability of indirect measurement (based on Maxwell equation) was critically analyzed with respect to the reliable direct measurement (based on heat flow). As evidenced in prototypical BNT-based compositions with different Td values, the dynamic behaviors of local polar structures including ferroelectric domains and polar nano-sized regions (PNRs), can largely affect the measured polarization and thus affect the reliability of indirect measurement. After systematically comparing and analyzing the composition-, temperature-, electric field (E-field)-dependent ECE results obtained from indirect and direct ways, the applicable working regions for the indirect method were determined. This work reveals the underlying mechanism behind direct and indirect ECE measurements, providing the “indirect + direct” experimental strategy for effectively evaluating the ECE performance in BNT-based relaxor ferroelectrics.

An Efficient Method for Laser Welding Depth Determination Using Optical Coherence Tomography.

Online monitoring of laser welding depth is increasingly important, with the growing demand for the precise welding depth in the field of power battery manufacturing for new energy vehicles. The indirect methods of welding depth measurement based on optical radiation, visual image and acoustic signals in the process zone have low accuracy in the continuous monitoring. Optical coherence tomography (OCT) provides a direct welding depth measurement during laser welding and shows high achievable accuracy in continuous monitoring. Statistical evaluation approach accurately extracts the welding depth from OCT data but suffers from complexity in noise removal. In this paper, an efficient method coupled DBSCAN (Density-Based Spatial Clustering of Application with Noise) and percentile filter for laser welding depth determination was proposed. The noise of the OCT data were viewed as outliers and detected by DBSCAN. After eliminating the noise, the percentile filter was used to extract the welding depth. By comparing the welding depth determined by this approach and the actual weld depth of longitudinal cross section, an average error of less than 5% was obtained. The precise laser welding depth can be efficiently achieved by the method.

Design, fabrication, and investigations of prototype supersonic micro-ejector for innovative cooling system of electronic components

Innovative approach for electronics cooling was proposed, i.e. heat generated by a part of electronic equipment, e.g. CPU, is absorbed by heat driven micro-ejector refrigeration system that can provide cooling of other electronic components, e.g. GPU. It was demonstrated the procedure of design, fabrication, and experimentation on the supersonic micro-ejectors for the case of isobutane as a working fluid for such system. It was demonstrated that it possible to design and fabricate the micro-ejector of cooling capacity in the range 3 W suitable for cooling of electronic equipment. For the discussed micro-ejector entrainment ratio obtained was app. 0.20 under conditions of the motive heat source temperature app. 60 °C and evaporation temperature app. 22 °C. There were demonstrated difficulties in fabrication of the supersonic ejector due to small dimensions of the motive nozzle as well as mixing chamber. Required throat diameter of the motive nozzle was less than 200 μm and the diameter of the mixing chamber was 260 μm. For reported tests conditions the boundary temperature of the on-design operation condition was between 21 – 25 °C. However, the operation of the micro-ejector under off-design operation regime was stable and repeatable. Micro-ejector tests required an indirect method of measurement of critical motive mass flow rate to be applied. The performance line of tested ejector fits to ejectors theory and meet the basic assumptions in terms of thermal capacity and operating temperature. CFD technique used for numerical predictions of the ejector performance fits to experimental measured values with acceptable accuracy.

Low-Cost Indirect Measurements for Power-Efficient In-Field Optimization of Configurable Analog Front-Ends with Self-X Properties: A Hardware Implementation

This paper presents a practical implementation and measurement results of power-efficient chip performance optimization, utilizing low-cost indirect measurement methods to support self-X properties (self-calibration, self-healing, self-optimization, etc.) for in-field optimization of analog front-end sensory electronics with XFAB 0.35 µm complementary metal oxide semiconductor (CMOS) technology. The reconfigurable, fully differential indirect current-feedback instrumentation amplifier (CFIA) performance is intrinsically optimized by employing a single test sinusoidal signal stimulus and measuring the total harmonic distortion (THD) at the output. To enhance the optimization process, the experience replay particle swarm optimization (ERPSO) algorithm is utilized as an artificial intelligence (AI) agent, implemented at the hardware level, to optimize the performance characteristics of the CFIA. The ERPSO algorithm extends the selection producer capabilities of the classical PSO methodology by incorporating an experience replay buffer to mitigate the likelihood of being trapped in local optima. Furthermore, the CFIA circuit has been integrated with a simple power-monitoring module to assess the power consumption of the optimization solution, to achieve a power-efficient and reliable configuration. The optimized chip performance showed an approximate 34% increase in power efficiency while achieving a targeted THD value of −72 dB, utilizing a 1 Vp-p differential input signal with a frequency of 1 MHz, and consuming approximately 53 mW of power. Preliminary tests conducted on the fabricated chip, using the default configuration pattern extrapolated from post-layout simulations, revealed an unacceptable performance behavior of the CFIA. Nevertheless, the proposed in-field optimization successfully restored the circuit’s performance, resulting in a robust design that meets the performance achieved in the design phase.

A new indirect measurement method of the electron temperature for the Proto-sphera's pinch plasma

This article presents a new method for estimating the electron temperature of the Proto-sphera's screw pinch. The temperature radial profile is obtained by a self-consistent modeling of a 1D MHD equilibrium along with a 0D power balance of the plasma column, given measurements and estimates of the axial pinch plasma current, of the plasma rotational frequency and, at the equatorial plane, of the electron density radial profile, of the edge poloidal magnetic field, of the edge electron temperature and of the neutrals pressure in the vacuum vessel. The plasma is considered in equilibrium with its neutral phase and in constant rotation. A MATLAB code has been developed with the aim of estimating the MHD radial equilibrium profiles, the thermodynamic plasma state and the neutrals profile. The numerical estimates are compared with available experimental data showing a good agreement.

Multicomponent Signal for Comparing Direct and Indirect Methods of Speech Transmission Index Measurement

When evaluating the intelligibility of speech distorted by noise and reverberation, direct or indirect methods of measuring the speech transmission index are used. However, it remains insufficiently studied how significantly differ the results of measurements obtained by direct and indirect methods. To find an answer to this question, the use of a multicomponent test signal consisting of four "elementary" signals separated by pauses is proposed in this paper. As "elementary" signals, it is proposed to use a maximum-length sequence, a speech shaped maximum-length sequence, a speech shaped stationary noise, and a speech shaped amplitude-modulated noise. Use of amplitude-modulated noise allows estimating speech transmission index by a direct method. Other "elementary" signals make it possible to estimate speech transmission index by two variants of indirect method. The proposed algorithms and corresponding computer programs were tested on trial signal models, while the consistency of the obtained results with the results of previous studies was revealed. The results of the signal models studies show that both considered variants of the indirect speech transmission index measurement method lead to underestimated results compared to the direct method. For one of the variants of the indirect method, the value of the estimate bias is 0.03–0.04, regardless of the interfering conditions. For another variant of the indirect method, the estimate bias varies from 0.01 to 0.18, depending on the interference conditions.

In-situ indirect measurements of real-time moisture contents during microwave vacuum drying of beef and carrot slices using terahertz time-domain spectroscopy

Moisture content (MC) is a critical quality indicator for food drying processing, however achieving in-situ non-destructive analyses of dynamic MC of products during processing is still a challenge. This study developed an in-situ indirect measurement method using Terahertz time-domain spectroscopy (THz-TDS) for real-time MC prediction of foods during microwave vacuum drying (MVD). During MVD, THz-TDS continuously sense the dynamic moisture vapour from the desiccator through a polyethene air hose. The obtained THz spectra were processed to calibrate MC loss prediction models using support vector regression, Gaussian process regression and ensemble regression. Then the MC was calculated using moisture loss prediction results. The best real-time MC prediction results for beef and carrot slices achieved R2 of 0.995, RMSE of 0.0162, and RDP of 22. The developed system provides a novel method for drying kinetics research during MVD and expands the applicability of the THz-TDS technique in the food industry.

Integration of Traction Electricity Consumption Determinants with Route Geometry and Vehicle Characteristics

Traction electricity (TE) consumption in rail transportation (rail transport) is determined by factors (determinant) related to the characteristics of railway lines and vehicles. They have an impact on driving speeds, which, in turn, affect energy consumption. The scientific research presented here combined the results of expert, direct and indirect measurement methods, including brainstorming, mind mapping, system approach, heuristics, failure mode and effect analysis. The main objective was to demonstrate the influence of the determinants of TE consumption, depending on the route (road) geometry and characteristics of the traction of electric vehicles and whole trains (catenary-supplied electric vehicles, non-autonomous electric vehicles, and network traction vehicles, especially electric locomotives and electric multiple units, electric multiple-units (EMUs)). Using a new approach, the TE consumption equation, we applied values for the movement resistances of electric locomotives during braking for a jointed railway track Mres JRT braking and continuous welded rail tracks Mres CWRt braking. The values of the movement resistances of the electric locomotives during startup on the jointed railway track Mres JRT startup and continuous welded rail tracks Mres CWRt startup were also applied. They showed a strong correlation with the existing speeds of catenary-supplied electric vehicles. The implementation of the new innovative approach is an important contribution to the development of engineering and technical sciences, in particular, the disciplines of civil engineering, surveying/geodesy, and transport.

Mesh shrinkage after transabdominal preperitoneal inguinal hernia repair

Synthetic mesh is now used for inguinal hernia repair in most cases. It is well known that the indwelling mesh contracts after placement in the body, regardless of the material. The aim of this study was to develop a method for indirect measurement of the mesh area postoperatively that allows for easy comparison with the condition of the mesh immediately after surgery. X-ray-impermeable tackers were used to fix the mesh, and changes of the indwelling mesh after surgery were measured indirectly using two mesh materials. This study involved 26 patients who underwent inguinal hernia repair with a polypropylene or polyester mesh (13 patients each). Polypropylene showed a stronger tendency to shrink, but there was no significant difference between the materials. For both materials, some patients showed relatively strong shrinkage and others showed relatively weak shrinkage. The group with the strong shrinkage had significantly higher body mass index. The results of the present study showed that mesh surly shrinked over time and there was no adverse effect of mesh shrinkage on the patients outcomes in this population. Mesh would shrink over time regardless of the sort of mesh but it did not affect the patients outcomes.

Configuration of the Geometric State of Railway Tracks in the Sustainability Development of Electrified Traction Systems.

The state-space interface of the railway track (track) geometry system with an electrified traction system (ETS) constitutes the geometric configuration that is utilised in this study. Importantly, driving comfort, smooth operation (smooth running), and compliance with the ETS are the desired aims. Direct measurement methods were used in the interaction with the system, especially in regard to the fixed-point, visual, and expert methods. In particular, track-recording trolleys were used. The subjects belonging to the insulated instruments also included the integration of certain methods, such as in the brainstorming, mind mapping, system approach, heuristic, failure mode and effect analysis, and system failure mode effects analysis methods. These were based on a case study and are representative of three real objects, i.e., electrified railway lines, direct current (DC), and scientific research objects (which specifically cover five research objects). The aim of the scientific research work is to increase the interoperability of the railway track geometric state configurations in regard to the sustainability development of the ETS. The results of this work confirmed their validity. By ensuring that the six-parameter defectiveness D6 was defined and implemented, the D6 parameter of the railway track condition was first estimated. The new approach reinforces the improvement in preventive maintenance and reductions in corrective maintenance; moreover, it is an innovative supplement to the existing direct measurement method in the configuration of the geometric condition of railway tracks and in the sustainability development of the ETS via interacting with the indirect measurement method.

Review of wheel-rail forces measuring technology for railway vehicles

In this paper, the research status of three types of wheel-rail interaction force measuring approaches, that is, IWS, ground measurement method and indirect measurement method, are summarized systematically. According to the measuring locations, the IWS can be determined by measuring the bending strain of the axle, as well as the strain of the wheel web. The measuring principle, bridge assembly method, calibration test and sensing technology of IWS are introduced respectively. This paper introduces the ground measurement method of measuring·wheel-rail force by arranging sensors on the rail and other track components to test their response, and the indirect methods for wheel-rail forces measurement are reviewed, which is derived from inertial force and suspension force of wheelset according to the force states of the wheelset. The advantages and disadvantages of the IWS, the ground measurement method and the indirect measurement method are analyzed. The investigation results show that the measuring principle of the IWS is relatively mature, and its measurement accuracy mainly depends on the manufacturing technology, bench calibration and signal acquisition. Future development of the IWS tend to realize the non-destructive, wireless, continuous and accurate measurement of the wheel-rail forces and contact points locations.

Indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement

The measurement method of ultrasonic bone cutting force is an urgent problem to be solved in the application of ultrasonic osteotome in robot assisted orthopaedic surgery. It is of great significance to realize bone layer perception and cutting force control in the process of surgery. In this paper, an indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement is proposed for the first time. Firstly, a one-dimensional numerical model for the interaction between ultrasonic osteotome and bone tissue is established. The model consists of two modules. The first module is the electromechanical model of ultrasonic osteotome, including piezoelectric transducer model and stepped horn model. The second module is the load model simulating ultrasonic bone cutting, which can be expressed by the Kelvin-Voigt model. The influence of load on the vibration characteristics of ultrasonic osteotome was studied by a one-dimensional numerical model. A full factorial design of experiment is used to collect the necessary data for developing and validating the models. Then, the indirect measurement model of ultrasonic bone cutting force is developed by using grey wolf optimized BP (GWO-BP) neural network algorithm. Taking the effective value x1rms and vibration frequency fx1 of anti-node vibration displacement as inputs, the effective value Frms of cutting force is output. It is found that the predicted effective value of cutting force is in good agreement with the corresponding numerical calculated effective value of cutting force. Finally, the continuous system of ultrasonic osteotome and bone tissue interaction is simulated by finite element method, the discrete system of ultrasonic osteotome and bone tissue interaction is simulated by physical method, and the experimental platform for indirect measurement of cutting force is built. The corresponding relationship between cutting force and anti-node vibration displacement is illustrated, which further verifies the effectiveness and feasibility of the indirect measurement method of ultrasonic bone cutting force based on anti-node vibration displacement.

Numerical calculation method of steam-liquid separation efficiency of the corrugated plate dryer based on the discrete phase model and the Euler water film model: A short communication

The corrugated plate dryer (CPD) is a sort of steam-liquid separation (SLS) equipment widely employed in energy and chemical industries, etc. Moreover, the steam-liquid separation efficiency of CPD, a crucial secondary SLS device of the nuclear power plant’s second loop, has a significant impact on the quality of the steam, which will indirectly affect the efficiency of energy conversion in the process that nuclear energy is converted into electronic energy. In practical engineering applications, it is necessary to give the steam-liquid separation efficiency (SLSE) value of CPD with different structural parameters according to different working conditions for the design and selection of CPD. At present, the SLSE of CPD is mainly measured based on some indirect measurement method such as conductivity measurement. However, this method generally requires the production of large amounts of CPDs. Meanwhile, successful structural design of CPD is based on extensive trials, which will consume a lot of time and research and development (R&D) expenses. Therefore, finding a solution to the problem of precise calculation of SLSE of CPD at present is urgent. The use of numerical simulations to realize this calculation has important engineering applications. In this paper, based on the coupling of Discrete Phase Model (DPM) and Euler Water Film (EWF) model, the precise calculation of the SLSE of CPD is realized. This is the first time that the academic community has obtained a precise calculation method for the Re-entrainment phenomenon (Maximum value of separation efficiency) of CPD, which can provide a very important technical support for CPD structure design.

Assessment of Financial Reporting Quality in a Developing Country Using Nice Qualitative Characteristics Measurement

Purpose: The use of different indirect measurement methods by prior empirical studies has led to contradictory findings about financial reporting quality. Therefore, this study assessed the extent of financial reporting quality using the direct method.
 Methodology: Data was collected through quantitative content analysis of annual reports and audited financial statements of 20 Zambian listed companies for the period 2012 to 2018 using a direct measurement tool developed by the Nijmegen Center for Economics (NiCE). Descriptive statistics were used to assess the extent of financial reporting quality.
 Findings: The study showed that the mean and median score for financial reporting quality is 2.62(52.3%) and 2.55(51%) respectively with a minimum of 2.06(41.2%) and maximum of 3.21(64.2%). The level of financial reporting quality was moderately low. Further, relevance and comparability of financial reports were poor, and companies used only or mostly historical cost instead of fair value as basis for measurement as proposed by the IFRS for its FRQ standard. Therefore, the financial reporting quality of listed companies do not meet all the criterion set out in the IFRS conceptual framework.

Introducing Spectrophotometry for Quality Control in Lithium‐Ion‐Battery Electrode Manufacturing

The demand for electrochemical storage systems is increasing due to their conventional use in mobile applications and potential as energy storage devices in power generation and electromobility. Due to its comparatively low weight and high energy density, the lithium‐ion battery is one of the most widely used electrochemical storage devices. Battery cell production consists of a complex process chain with a large number of interdisciplinary processes. Each process step has specific requirements for the product. Different process parameters are essential in each step and require unique control measurements to ensure the quality of the intermediate product. To identify critical parameters, an understanding of the potential effects of different process parameters and the relationship between structural characteristics and end product properties must be gained. Therefore, herein, spectrophotometry concerning its application in lithium‐ion battery production is investigated. Individual process steps in electrode production are carried out to establish a correlation between intermediate product properties and measured color values. The influences of the powder components, the dispersion, and coating process are discussed. Based on the experiments carried out in this study, the suitability of spectrophotometry as an indirect measurement method of intermediate product properties is demonstrated.

Safety Monitor Symmetry Concerning Beam Bridge Damage Utilizing the Instantaneous Amplitude Square Method

It is critical for the safety monitoring of highway bridges that beam bridge damage can be identified from the dynamic response of passing vehicles. Numerical simulations of passing vehicles were conducted utilizing the vehicle–bridge coupling vibration theory and the indirect measurement method. Fast Fourier transform was performed on the time history response of vehicle acceleration, and the driving frequency component response and its instantaneous amplitude square value (IAS value) were obtained by band-pass filtering and Hilbert transform processing. The identified IAS value detected the damage location of the bridge. The identification method of IAS value is used to analyze the applicability of a simply supported beam bridge, a continuous beam bridge, and an irregular skew beam bridge. The effects of vehicle speed, vehicle damping, bridge damping, and a social vehicle on damage identification are discussed. The results show that the effect of damage location is better when the vehicle speed is less than 4 m/s. In the presence of social vehicles, the excitation on the bridge increases, and the damage location can still be accurately determined by the IAS method. Vehicle damping and bridge damping have little effect on the results of damage identification. In structural health monitoring for bridges, this paper can provide a theoretical reference for the application of IAS motion sensing to identify the damage location indirectly.

Determination of Particle Size Distributions of Bulk Samples Using Micro-Computed Tomography and Artificial Intelligence.

The knowledge of product particle size distribution (PSD) in crystallization processes is of high interest for the pharmaceutical and fine chemical industries, as well as in research and development. Not only can the efficiency of crystallization/production processes and product quality be increased but also new equipment can be qualitatively characterized. A large variety of analytical methods for PSDs is available, most of which have underlying assumptions and corresponding errors affecting the measurement of the volume of individual particles. In this work we present a method for the determination of particle volumes in a bulk sample via micro-computed tomography and the application of artificial intelligence. The particle size of bulk samples of sucrose were measured with this method and compared to classical indirect measurement methods. Advantages of the workflow are presented.

Real-time estimation of thermal boundary conditions and internal temperature fields for thermal protection system of aerospace vehicle via temperature sequence

Aerospace vehicles go through extremely aerothermal heating upon entry into the atmospheric, which need to employ the reliable thermal protection system (TPS). The boundary heat flux and inner temperature information for aerospace vehicles are required to design the TPS. The direct measurement for temperature and heat fluxes is quite difficult mission. In this study, unscented Kalman filtering, is an indirect measurement method based on inner surface temperature information and is introduced to reconstruct the transient heat flux and inner temperature fields of TPS in real-time, which is regarded as a graded index medium. The finite volume method and discrete ordinate method are utilized to solve the energy equation and radiative transfer equation to obtain measurement temperature, respectively. Based on the measurement temperature signal, the unscented Kalman filtering technique is applied to reconstruct the surface heat flux and inner temperature field of the TPS. Simulation results indicate the time-dependent boundary heat flux and inner temperature fields can be estimated using proposed method. The effects of thickness, refractive index, measurement noise, and process noise on the reconstructed results are studied in detail. Retrieval results show the proposed technique is more precise and robust than Kalman filtering method in the nonlinear system.

Real-time wheel–rail friction coefficient estimation and its application

The friction coefficient at the wheel–rail interface is crucial for the traction, braking and guidance of the railway vehicle. Real-time knowledge of the friction coefficient could reduce wheel–rail damages as well as improve the vehicle running performance. The friction coefficient is very difficult to be directly measured; hence an indirect measurement method using an unscented Kalman filter was proposed in this paper. A re-adhesion controller was also developed. The method was assessed in a Simpack-Simulink co-simulation environment. The friction coefficient estimation method was found to be accurate, and the re-adhesion controller improved the vehicle braking performance as well as reduced the wheel–rail damage.

Introduction of a new French beer brand on the Polish market in the opinion of consumers

Objective: The study aims to identify the behavior, opinions, motives and expectations of Polish consumers towards beer brands, with a particular focus on a beer brand manufactured by a French brewery. The consumer survey carried out allows identification of several major potential consumer groups to be targeted by a medium-sized independent French brewery with its offer. Methodology: The study employed the use of primary sources obtained via a measurement instrument, in the form of an online survey questionnaire, developed for the purpose of the ResearchLab 2022 academic contest organized by Le Sphinx. The consumer survey was conducted in the period from April 12 to May 01, 2022. A method of indirect measurement, i.e., a survey questionnaire, was used to collect the material, which allows collection and examination of data on large research populations. The questionnaire consists of introductory questions regarding the beer market in Poland, consumer behavior questions concerning consumer awareness, preferences and consumption motives, questions pertaining to market barriers and foreign beer brands, as well as a metric part. The research process involved the use of Sphinx software, which allows intuitive development of a survey questionnaire, its quick distribution, convenient collection of data, as well as comprehensive quantitative and qualitative analysis thereof. The platform additionally allows for real-time tracking of the survey results, which quite is important when conducting research on a well-defined study group. The survey encompassed a research population of 3792 respondents (male and female) of different age ranges. The sample size was determined on the basis of Internet accessibility in Poland (92.4%, in 2021) (2021 Information Society in Poland…, 2021, p. 125). In order to maintain result representativeness, the minimum number of survey participants was calculated at 2401 respondents, assuming a confidence level of 95% and an error of 2%. The representative sample was of a quota nature, defined by the contest holder, and encompassed 40% of respondents aged 18-35 and 36-55 respectively, as well as 20% of respondents over 56 years of age. Gender-wise sample distribution was 60% males and 40% females. The data was examined using such statistical methods as structure analysis, as well as positional or classical measures. Results: The survey results show that the preferred beer package size is 500ml glass bottle, with an alcohol content of 3.6% to 7%. The main Polish market competition for the French independent brewery's new beer brand are Lech, Żywiec, and Desperados. The preferred beer types are lager (72%), IPA (47%) and flavored beer (47%). The beer flavors most commonly chosen by consumers on the Polish market are lemon and lime, mojito, apple and honey. An ideal beer, as typified by the respondents, would be characterized by average proportions of aroma, color, carbonation, bitterness and alcohol content. The factors prompting consumers to try new beer brands are primarily taste, price and advertising, therefore, it is worth focusing on the three, maintaining proportions in the order in which the factors have been presented. Information regarding alcohol novelties most commonly is derived from friends or Social Media, which is why advertising should involve the use of these channels for e.g., various types of Facebook, Instagram, Youtube, Tik Tok contests. The respondents reacted positively to the French beer brand, and the majority would opt to try this type of beer, given the opportunity. Their expectation with regard to the brand is high price, good quality and taste, as well as elegance. Its envisioned label design is associated with the national colors of France, the city of Paris, Napoleon, and the Alps. It is thus worth taking the above associations into account when designing the label. Originality: The article presents the consumer opinions regarding introduction of a new French product on the Polish market. It is addressed to distributors of imported beer. Key words: beer, beer market in Poland, France, French brewery. Article category: Research Paper.