Radio Frequency Identification Applications Research Articles

High Directivity Microstrip Patch Antenna design using Binary Ebola Search Optimization for Radio Frequency Identification Application

Microstrip patch antenna has gained significant popularity in wireless communication field, because of its compact size, less profile, and ease of installation. It is widely used in various applications such as Radio-Frequency Identification (RFID) systems, where dependable and long-range communication is made possible by the great directivity and efficiency. In this manuscript, a High Directivity Microstrip Patch Antenna design using Binary Ebola Search Optimization for Radio Frequency Identification Application (MPA-RFID-BESO) is proposed.The design of microstrip patch antennas is the difficulty in achieving high directivity while maintaining compact size and low profile. This research explains design and application-specific optimisation of the Microstrip Patch Antenna (MPA) of biomedical utilizing Binary Ebola Search optimization (BESO) algorithm. Microstrip patch antenna is designed to function in double and multi band applications due to its low cost, light weight, and ease of installation. MPA is made with flawed ground construction to lessen cross-polarized radiation emitted by microstrip patches and to achieve the necessary radiation parameters. Here, the cost of the materials is reduced by using a liquid crystal polymer substrate, and aerial performance is enhanced by using the appropriate geometrical parameters. The small design of the BESO optimised improves the performance of antenna as 50mm×50mm compact size. The MATLAB program uses high frequency to do the simulation method. The proposed antenna design is a preferable option for applications involving Radio Frequency Identification (RFID). The performance metrics, such as radiation pattern, constant gain, directivity, bandwidth, and antenna efficiency and return loss are measured and compared to the existing techniques. The proposed MPA-BA-BESO design provides 10.51%, 12.85% and 16.04% higher bandwidth and 23.63%, 47.86% and 32.06% higher gain compared with existing designs, like Designing MPA utilizing Moth–Flame optimization approach (MPA-UWB-MFOA), Predicting Rectangular Patch Microstrip Antenna Dimension utilizing Machine Learning (MPA-ANN), Dual Band Antenna Design and Prediction of Resonance Frequency Utilizing Machine Learning Algorithms (DBAD-RF-CNN) respectively. The proposed technology serve as a better design alternative for microstrip patch antennas in communication systems to address biological applications.

A Low-Profile Electrically Small Serrated Rectangular Patch Antenna for RFID Applications

This paper presents the design and analysis of a global system for mobile communication applications, as well as the design and analysis of a compact, bidirectional Electrically Small Antenna (ESA) at 0.9 GHz for Radio Frequency Identification (RFID) applications. In order to attain results at lower frequencies while keeping a compact size, the proposed design consists of a microstrip patch antenna in which an SRR and a semicircular-shaped SRR were subtracted from the ground plane. The dimensions of the FR4 substrate, on which this ESA was designed, were 20 × 18 × 1.6 mm. Ansys HFSS was used for the design and simulation of the antenna. Chemical etching was implemented to fabricate the ESA and MS2037C Anritsu Combinational Analyzer was applied for testing. The simulated results show that at 0.9 GHz, the ESA achieves a bandwidth of 300 MHz (700 MHz-1000 MHz). At the resonance frequency, a bidirectional radiation pattern with a 80% radiation efficiency is obtained in both H and E planes. A 90% agreement between the simulated and the fabricated results has been achieved.

Novel printed passive ultra high frequency radio frequency identification antenna using meander technique

<p>In this paper, a novel radio frequency identification (RFID) antenna using a meander technique associated with a slotted patch is studied for RFID applications in the ultra high frequency (UHF) band [867.5-868 MHz]. The proposed RFID antenna is designed on a Kapton substrate with dielectric constant 3.5 and loss of 0.0027. It consists of two opposite meander line antennas of 8 turns each one and interconnected to ALIEH H3 microchip associated to two slotted patch’s with a global size 105×25×0.1 mm<sup>3</sup>. The proposed RFID antenna is designed and simulated using CST MWS as an electromagnetic solver. The results of the simulation show a return loss of -22.64 dB at 868 MHz, a reading distance of around 5 m, and a simulated input impedance of the antenna are 31.72+j109.68 Ω at the operating frequency 868 MHz.</p>

RFID tag recognition model for Internet of Things for training room management

With the rapid development of the Internet of Things and intelligent technology, the application of Radio Frequency Identification (RFID) technology in training room management is becoming increasingly widespread. An efficient and accurate RFID system can significantly improve the management efficiency and resource utilization of the training room, thereby improving teaching quality and reducing management costs. Although RFID technology has many advantages, there are still some problems in practical applications, such as label collision and recognition of unknown labels. These issues not only affect the performance of the system but may also cause interference with actual teaching and management. This study proposes a grouping-based bit arbitration query tree algorithm and anti-collision technology to solve label collisions and reduce label recognition time in the technology. A new unknown label recognition algorithm is also proposed to improve the recognition efficiency and accuracy of identifying new unknown labels. Related experiments have shown that the recognition accuracy of the algorithm designed this time is 95.86%. Compared with other algorithms, the number of idle time slots is the smallest. When the number of queries is 1000, the algorithm has 1842 queries, and the communication complexity is the best. When the number of unknown tags is 10,000, the actual accuracy rate is 95.642%. Compared with traditional recognition algorithms, the new unknown label recognition algorithm has a smaller frame length in the same label proportion and good recognition performance. On a theoretical level, the research content on RFID technology helps to improve and develop the basic theories of the Internet of Things and intelligent recognition technology and provides solutions and application technologies for equipment management and IoT applications in training rooms. On a practical level, the research results can provide specific guidance for the management of training rooms, help solve equipment management and safety maintenance problems in practical applications, and improve the management efficiency of training rooms.

Analysis of a Compact Electrically Small Antenna with SRR for RFID Applications

This paper contains the design and analysis of a compact, bidirectional Electrically Small Antenna (ESA) at 0.9 GHz for Radio Frequency Identification (RFID) and a global system for mobile communication applications. The proposed design consists of a microstrip patch antenna enclosed inside the split ring resonators, in which a split ring resonator was subtracted from the ground plane in order to obtain the results at lower frequencies by maintaining a compact size. This ESA was designed on FR4 substrate having a dimension of 30 mm × 30 mm × 1.6 mm. This antenna was created and simulated with the Ansys HFSS. The ESA was fabricated by chemical etching and it was measured with the MS2037C Anritsu Combinational Analyzer. The simulated results show that the ESA attains a bandwidth of 100 MHz (with S11 < -10 dB) at 0.9 GHz. The bidirectional radiation pattern in both H and E planes with a radiation efficiency of 80% at the resonant frequency was obtained. A close agreement of 90% between the simulated and the measured results was observed.

Design and Analysis of a Quad-Band Antenna for IoT and Wearable RFID Applications

The role of antennas in wireless communication is critical for enabling efficient signal transmission and reception across various frequency bands, including those associated with IoT (Internet of Things), X-band, S-band, and RFID (radio-frequency identification) systems. This paper presents a small quadruple-band antenna with 25 × 40 × 1.5 mm3 dimensions designed for diverse wireless applications. It is adept at operating in the S-band (2.2 GHz), wireless local area network (WLAN) (5.7 GHz), microwave RFID frequency band (5.8 GHz), and X-band (7.7 GHz and 8.3 GHz). While the majority of existing research focuses on antennas covering two or three bands, our work stands out by achieving quad-band operation in the proposed antenna design. This antenna is constructed on a semiflexible Rogers RT5880 substrate, making it well-suited for wearable applications. Computer Simulation Technology (CST) Microwave studio (2019) simulation package software is chosen for design and analysis. The antenna design features a comb-shaped radiating structure, where each “tooth” is responsible for resonating at a distinct frequency with an appropriate bandwidth. The antenna retains stability in both free space and on-body wearability scenarios. It achieves a low specific absorption rate (SAR), meeting wearable criteria with SAR values below 1.6 W/Kg for all resonating frequencies. The proposed antenna demonstrates suitable radiation efficiency, reaching a maximum of 82.6% and a peak gain of 6.3 dBi. It exhibits a bidirectional pattern in the elevation plane and omnidirectional behavior in the azimuth plane. The antenna finds applications across multiple frequencies and shows close agreement between simulated and measured results, validating its effectiveness.

Magnetic Permeability Perturbation-Based RFID Sensor for Pipeline Internal Corrosion Monitoring

Radio frequency identification (RFID) sensors for pipeline corrosion monitoring have been considered an attractive area due to the advantages of battery-free and maintenance-free. Due to the skin effect of high-frequency electromagnetic waves, existing RFID sensors can only detect the surface corrosion of pipelines. To realize internal corrosion monitoring, a magnetic permeability perturbation-based RFID sensing method was developed in this paper. Under direct-current (DC) magnetization, internal corrosion causes magnetic field distortions and incurs magnetic permeability perturbations in the skin layer of surface. These perturbations can be detected by the RFID sensor. Considering the resonance frequency shift (RFS) as a feature, a patch antenna sensitive to magnetic permeability was designed. Moreover, steel plates with artificial internal defects were simulated and tested to validate the feasibility of the proposed method. It was observed that the surface magnetic permeability perturbations caused by internal corrosions of different depths incur different RFS values. Finally, pipelines with artificial and natural internal corrosions were tested to validate the feasibility of the proposed method. The RFS caused by the natural corrosion was 4.26 MHz, and the RFS caused by the sound area was 1.63 MHz. The proposed magnetic permeability perturbation-based RFID method provides a promising method for pipeline internal corrosion monitoring with the application of RFID sensing technology.

Application Analysis of RFID in Supply Chain Management

With the increase in global trade and the intensification of market competition, the importance of supply chain management is becoming more and more obvious. Radio Frequency Identification (RFID) technology emerged as the times required, bringing a new solution to supply chain management. This article will discuss the application analysis of RFID in supply chain management. The article mainly analyzes the environmental benefits of RFID technology; RFID application analysis based on the clothing industry and the application of RFID technology in inventory management of companies. The results of the study pointed out that although there are still some difficulties in the application of RFID technology, RFID technology has indeed effectively improved the efficiency of the supply chain. Moreover, the development trend of RFID is getting better and better, and the RFID technology has gradually lowered the application threshold standard as more people invest in research. RFID ultimately brings more benefits to enterprises and society. Therefore, this paper proposes to increase investment in the application of RFID technology in the supply chain. This article aims to provide decision-making guidance and reference significance for enterprises using RFID technology.

An Optimized Temperature Compensated Ring Oscillator with Low Power Consumption and Low Variation

In this paper a low power ring oscillator with three differential delay stages and one output buffer stage is designed for Radio Frequency Identification (RFID) applications. The proposed oscillator is designed with neural network model and its parameters are optimized with Teaching–Learning Based Optimization (TLBO) algorithm. The central frequency of the oscillator becomes independent of the temperature with the help of two temperature compensation techniques. In the first technique, the PMOS load transistor of each stage is connected to the NMOS diode connected - in series - transistor. Since these two transistors work in complement of each other, the temperature variation of each stage’s output voltage is decreased. In the second technique, the current variation of oscillator stages versus temperature is reduced since the diode connected transistor is employed in the current source structure. The simulation is done in 0.18 µm Complementary Metal-Oxide Semiconductor (CMOS) technology with the help of Cadence software and the chip area of the layout designed with this software is 19×25 µm2. The designed oscillator exhibits the following parameters: a central frequency of 7.5 MHz, the power dissipation is 238 nW and the frequency deviation is 210 ppm/̊C in the temperature range of 0 to 120ºC, the noise phase and the period jitter are -87.05 dBc/Hz and 0.578 ns (rms), respectively, at 100 KHz offset frequency and 10000 clock cycle.

Critical application areas of radio frequency identification (RFID) technology for sustainable construction in developing countries: the case of Nigeria

Purpose This study aims to explore the critical application areas of radio frequency identification (RFID) technology for sustainable buildings. Design/methodology/approach The quantitative research approach was adopted through a structured questionnaire administered to relevant stakeholders of construction projects. The data collected were analysed with the exploratory factor analysis, relative importance index (RII) and fuzzy synthetic evaluation (FSE). Findings The study’s results have categorised the crucial areas of application where construction industry stakeholders should focus their attention. These areas are divided into four categories: management technologies, production technologies, sensing technologies and monitoring technologies. The findings from the FSE indicate that monitoring technologies represent the most significant category, whereas management technologies rank as the least significant. Moreover, the RII analysis highlights that tools management stands out as the most important application of RFID, while dispute resolution emerges as the least significant RFID application. Practical implications The study establishes the core areas of RFID application and their benefits to sustainable buildings. Consequently, it helps stakeholders (consultants, clients and contractors) to examine the RFID application areas and make informed decision on sustainable construction. Furthermore, it provides systematic proof that can aid the implementation of RFID in developing countries. Originality/value The study provides an insight into the possible application areas and benefits of RFID technology in the construction industry of developing countries. It also developed a conceptual frame for the critical application areas of RFID technology in the construction industry of developing countries.

A compact meander flexible UHF tag for industrial applications

The objective of this paper is to introduce a novel design for a flexible Ultra-High Frequency tag (UHF tag) through the utilization of the meander line technique (MLA) and loop antenna method. The primary goal is to achieve a compact UHF tag operating at 868 MHz. The physical dimensions of the UHF tag are 110×12×0.1mm3. The proposed UHF tag is manufactured using the inkjet printing method on a polyamide substrate featuring a relative dielectric constant of 3.5, a tangent loss of 0.0027, and a height of 0.0508 mm. Through electromagnetic simulation and validation, the functionality of the proposed UHF tag covers the UHF band ranging from 854.57 to 883.89 MHz, with a bandwidth of 29.32 MHz. The reflection coefficient at 868 MHz is approximately -22.46 dB. The simulated gain measures 1.79 dBi, while the theoretical read range is estimated at 5 m. The UHF tag is produced using silver ink with a thickness of 0.05 mm and assembled using an anisotropic conductive paste (ACP). Subsequent to electromagnetic simulation, the UHF tag’s performance is confirmed through a reading test conducted with a radio frequency identification (RFID) base station. The results are consistent with the theoretical expectations, showcasing a commendable read range of 5 m. To safeguard the UHF tag from challenging environmental conditions, it is enclosed within a polyethylene film (PE). Following encapsulation, the read range decreases to 3 m, making it suitable for RFID applications requiring mid-range capabilities.

Design of 2.45GHz Circularly Polarized Tag Antenna

This paper presents the design and development of a circularly polarized (CP) tag antenna to overcome the polarization mismatch between the reader antenna and the tag antenna in RFID systems. This CP antenna is designed at 2.4 GHz for radio frequency identification (RFID) applications. It consists of a simple square loop loaded with an open gap, two feeding strips, and a matching stub. The antenna is fabricated on an FR4 substrate with a dielectric constant of 4.4, a dielectric loss tangent of 0.02, and a thickness of 0.8mm. In order to achieve conjugate matching between the circular tag antenna and the tag chip, the technique of loading a matching short line on the tag chip was used. Additionally, the radiation of circular polarization (CP) was achieved by placing an open gap and two feeding strips on the square loop. Through electromagnetic simulation analysis, the antenna performance is evaluated. The reflection coefficient (S11) at 2.45 GHz is measured to be - 17.16db, indicating good impedance matching. The 3 dB axial ratio bandwidth is 0.19 GHz (7.7%), covering the frequency range of 2.34 GHz to 2.53 GHz. The 10db power reflection bandwidth is approximately 8.9% (2.33 GHz to 2.55 GHz), ensuring broad operational bandwidth. The antenna also exhibits a favorable antenna gain of 2.29dBi. This study successfully demonstrates the design and performance evaluation of a CP tag antenna for RFID applications

Nature-inspired spider web shaped UHF RFID reader antenna for IoT and healthcare applications

This paper proposes a nature-inspired spider web-shaped ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna and battery-free sensor-based system for healthcare applications. This antenna design consists of eight concentric decagons of various sizes and five straight microstrip lines.These lines are connected to the ground using 50 Omega resistors from both ends, except for one microstrip line that is reserved for connecting a feeding port. The reader antenna design features fairly strong and uniform electric and magnetic field characteristics. It also exhibits wideband characteristics, covering whole UHF RFID band (860–960 MHz) and providing a tag reading volume of 200 times 200 times 20 mm{^3}. Additionally, it has low gain characteristics, which are necessary for the majority of nearfield applications to prevent the misreading of other tags. Moreover, the current distribution in this design is symmetric throughout the structure, effectively resolving orientation sensitivity issues commonly encountered in low-cost linearly polarized tag antennas. The measurement results show that the reader antenna can read medicine pills tagged using low-cost passive/battery-free RFID tags, tagged expensive jewelry, intervenes solution, and blood bags positioned in various orientations. As a result, the proposed reader antenna-based system is a strong contender for near-field RFID, healthcare, and IoT applications.

Barcode andradio frequency identification utilization varied across Korean hospitals.

Barcodes and radio frequency identification (RFID) are increasingly used in health care to improve patient safety. However, studies on their utilization in clinical settings are limited. This study aimed to comprehensively examine the utilization status of barcodes and RFID in Korean hospitals, recognize the effects and obstacles associated with utilization, and explore the measures to expand the applications of barcodes and RFID. A self-reported online survey was conducted in tertiary hospitals, general hospitals, hospitals, and nursing hospitals in the Republic of Korea. The survey questionnaire comprised questions on barcodes and RFID utilization status, the effect of barcodes and RFID utilization, measures to expand the utilization of barcodes and RFID, and information on respondents' demographics and hospitals. A representative from each of 23 tertiary hospitals, 101 general hospitals, 232 hospitals, and 214 nursing hospitals completed the survey (total response rate 17%). The data were analysed using the chi-square test or Fisher's exact test to determine the differences in responses based on the type and characteristics of hospitals. The tertiary hospitals had the highest utilizations of both RFID and barcodes (n = 10, 43.5%), whereas the nursing hospitals had the lowest (n = 96, 55.1%). Barcodes and RFID were most commonly used in the visits and security management domains. However, the use of barcodes and RFID in medication dispensing and administration safety was low, despite its value in improving patient safety. The hospitals recognized the positive effect of utilization of barcodes and RFID, reporting the highest frequency for the prevention of patient safety incidents (n = 79, 85.9%). Nevertheless, the cost of barcodes and RFID facility investments (n = 128, 90.3%) appeared to be the greatest obstacle to the introduction of barcodes and RFID. Hence, barcodes and RFID facility investment support (n = 133, 95.5%) were given the highest priority among the measures to expand barcode and RFID utilization in health care. The utilization of barcodes and RFID varied across the type and domain of hospitals in the Republic of Korea. Hospitals recognized the positive effects of barcode and RFID utilization. Nonetheless, all hospitals were concerned about the cost of investment and maintenance of barcode and RFID facilities as the main obstacles to utilization. Therefore, a support plan must be developed for the cost of barcodes and RFID facility investments to expand barcode and RFID utilization in health care.

Comprehensive Review on Multiresonator-Based Chipless RFID Tag

This study reviews the multi-resonator-based chipless radio frequency identification technology. Radiofrequency (RF) waves are used in a wireless data collecting technique called radio frequency identification or simply RFID to automatically identify things. RFID is a promising technology that enables the identification and tracking of objects. Because of its benefits, including cheaper cost, smaller size, and higher security, chipless Radio Frequency Identification (RFID) technology has become more and more attractive as a potential alternative to traditional RFID technology. Chipless RFID labels are minimal expense labels since they are not outfitted with ASIC. RFID transmits data between the RFID transponder, a device that carries data, and the interrogator using radio frequency (RF) waves. The system is completely passive and does not require any kind of outside power source to run. The major advantage of spectral signature-based chipless RFID is that it can encode data in both magnitude and phase. A transponder's essential parts are its transmitter, receiver, and multi-resonators. As a result, this article will evaluate different multi-resonator types, explore numerous chipless RFID applications, and discuss the basic operation of an RFID system. Additionally, this research studies the various coding systems because information coding is an essential part of this technology.

The role of RFID to improve supply chain sustainability: A systematic literature review and key informant survey

This paper presents a systematic literature review on the application of Radio Frequency Identification (RFID) technology for sustainability purposes in various supply chains while primarily focusing on the pharmaceutical supply chain. The review takes into consideration sustainability from an economic, environmental, and social perspective and investigates the various aspects of such a system from both the manufacturer and consumer points of view. The paper highlighted the importance, process, and effects of implementing RFID technology in the pharmaceutical supply chain to create a more sustainable and traceable system. The lack of strong scientific studies in the field of sustainability impacts of RFID-enabled pharmaceutical supply chain was identified. In addition to the literature review, this paper also takes into account results from an original survey conducted with current industry professionals and their views on sustainability in the pharmaceutical chain. The review’s findings can help frame future work and fill the gaps in the literature focusing on the sustainability impact of RFID technology in the pharmaceutical and healthcare supply chain.

Circular Polarized Antenna with Rotationally Positioned Microstrip Structures For UHF RFID Applications

With the use of wireless communication and the industry 4.0 revolution, RFID technology integration in production has increased. The large-scale preference of RFID systems is both cost-effective and significantly increasing production. It is an innovation that provides convenience for large production facilities such as product control, in-plant tracking, storage, inventory operations. In this paper, a compact circularly polarized (CP) reader antenna is presented for ultra-high frequency (UHF) radio frequency identification (RFID) applications. The proposed antenna consists of a circularly slotted ground plane and folded plus-shaped structures with vertical and horizontal positions. Microstrip line feeding technique is used in the vertically folded plus-shaped structure positioned on the front surface. The antenna has a 10 dB return loss bandwidth of 80 MHz (840-920) and a 3 dB axial ratio bandwidth of 20 MHz (855-875). Theproposed antenna has dimensions of 75 × 75 × 1.6 mm3 . The size advantage of the single-layer and singlefed structure enables its applicability in portable systems.

Supporting National Food Security Through the Implementation of Radio Frequency Identification (RFID) in the Warehouses of Badan Urusan Logistik

As many as 20,000 tons of rice in 2019 were discarded from the Logistics Agency (BULOG) warehouses due to their declining quality, making them unfit for consumption. The cause of rice damage is that the storage owned by BULOG is not a special warehouse for storing rice. This study aims to analyze BULOG rice storage and formulate ways to improve rice quality in realizing food security The method used in this research is qualitative approach and data collection using Focus Group Discussion (FGD) involving 15 people in the Edu Logistics Hub community. The application of Radio Frequency Identification (RFID) which processes information from rice stored in warehouses can minimize human error. The decline in the quality of rice in BULOG warehouses can be overcome by applying the First In First Out (FIFO) method and the application of RFID technology.

Wearable Ungrounded Tag Antenna for UHF RFID Applications

A single-layer ungrounded tag antenna is designed for on-body radio frequency identification (RFID) applications in the ultrahigh frequency (UHF) band. The ungrounded tag antenna is designed based on a broadside radiating Huygens source. The electric dipole is generated by the center part of an original dipole, while two orthogonal magnetic dipoles are created by stacking another two metallic strips at the edge of the original dipole. The tag antenna shows good robustness of input matching and radiation efficiency with respect to the human-body effect. Furthermore, the designed tag antenna is also able to work with metallic objects and its resonant frequency is stable around 920 MHz. Finally, three tag prototypes, including the proposed tag antenna, are fabricated and tested. The measured reading range confirms the numerical simulations and demonstrates the robustness of the proposed design with respect to different distances between human-body and tag antenna. The proposed tag provides a reading range of 5.0 m (near-body), 8.0 m (free space), and 16.5 m ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200\times200$ </tex-math></inline-formula> mm metallic plate), respectively.

Utilization Of Rfid In Building An Order Of Administration And Distribution In Material Warehouse Installation Gatot Soebroto Hospital Indonesia

RSPAD Gatot Soebroto is a type A government hospital with the highest referral in the ranks of the TNI and serves as a health service for the general public and continues to strive to improve the quality of excellent health services for each patient. For this reason, the Gatot Soebroto Army Hospital always provides medical supplies generally stored in the material warehouse installation. The Gatot Soebroto Army Hospital's material warehouse installation consists of a general and Health material warehouse. For health services to run well, improving the quality of the material warehouse installation unit is necessary. The development of Radio Frequency Identification (RFID) technology is increasing rapidly from year to year; its benefits can be integrated into managing material warehouse installations to build orderly administration and distribution of material medical supplies needed in each installation unit at the Gatot Soebroto Army Hospital. Through the warehousing application with the RFID application, it is hoped that the process of procurement, receipt, storage, and distribution of material for medical supplies will be more easily controlled, both for evaluation of use, as well as evaluation of stock-taking of supplies which will later become the basis for material procurement for the following year. In addition, RFID also controls the material distribution designation and year of procurement. So that the distribution of material as hospital assets will be recorded accurately and the health services provided can also run well and have good quality.