Aluminum Shaft Research Articles

An Experimental Investigations on Design and Weight Optimization for a Light Motor Vehicle (LMV) Drive Shaft Using a Composite Material Aluminum and Glass Fiber (Al + GF)

Aluminum is primarily used in Metal Composites because of its lighter weight and higher strength. Glass fibers are wound around an aluminum shaft to create the composite. ANSYS results determine the relative amounts of aluminum and Eglass fiber in each shaft. The purpose of this study is to use a torsion test to evaluate the mechanical performance of a composite shaft composed of aluminum and glass fiber. The results are carefully examined for different combinations of glass fiber layers and aluminum layers. When the weight proportion of aluminum in the composite increases, the mechanical properties of the composites improve.

Design, construction and performance analysis of dynamic torque transducer

Most of the dynamic torque measurement devices present are not easy to afford and accurate for higher shaft speed, at the same time, especially in the case of Micro-hydropower stations where dynamic torque fluctuates and requires constant monitoring. To fulfill the lack of standard devices, this project concentrated on fabricating non-contact torque transducer devices using easily accessible materials. The project primarily focuses on developing electronics and mechanical systems required to measure dynamic torque. The hollow Aluminum shaft is taken as a torque transducer specimen with a coupling facility. A strain gauge is attached with the specimen shaft in the Wheatstone bridge arrangement such that the strain gauge produces an electrical signal while the shaft experiences strain. Arduino NANO as an I/O device, HX711 ADC module as a signal amplifier, HC05 as a Bluetooth module for wirelessly measured data communication. For calibration, torque is applied to the specimen by coupling it with motor-generator dynamic torque measurement apparatus (DL 10055ETM) which is manufactured by DE LORENZO. Linear regression is used to predict the value of applied torque. The experimental data obtained using the proposed torque transducer prototype has made it clear that it is possible to measure and analyze real-time digital data of dynamic torque produced on specimen shaft rotating at high speed, wirelessly, using locally available resources.

Time-based dry cleaning brush controller for PV energy yield enhancement

Photovoltaic (PV) cleaning systems are getting popular to clean their dusty and sticky surface developed by foreign particles with morning dew and light rain. However, a non-automated PV cleaning system requires human intervention, time, and cost and is often not feasible for large PV generations. Current studies investigate different types of automated cleaning systems, which are being deployed to overcome such dust problems ranging from wet to dry cleaning. Exposure to different types of automated PV cleaning systems has been shown in other studies to be related to adverse effects in overcoming dust problems. Such approaches, however, have failed to address the sticky layer of dust and foreign particles accumulated on PV surfaces. This paper presents the development of a time-based PV cleaning brush controller that is operated through an automatic periodical time activation method. This study focuses on the mechanical design of the brush controller encompasses two carrier and one rotating motors, nylon brush in aluminum structured frame, hollow aluminum shaft, linear rails, real time clock (DS1307), and Arduino Uno microcontroller. A self-designed small-scale test-bed of 100W PV module was installed on a rooftop of a room within the premises of Universiti Tun Hussein Onn Malaysia (UTHM), Johor, Malaysia. The functional time-based cleaning brush controller was configured to operate at a frequency of five cleaning cycles per day without human intervention within the test-bed. It is a dry cleaning approach without any soapy water employment to realize the multiple cleaning cycles every day at 7A.M. within the overall testing. Results indicate that dust accumulation has a substantial effect on the PV performance on a timescale of seasons in this location. In addition, the system achieved a 72% of dust removal rate from the 5 cycles, whilst it is 80.6% at its 10 cycles of cleaning. Overall, the result shows that the energy yield of PV with the cleaning system is enhanced by 26% more than that of the unclean PV. The cleaning system design can be very effective for rooftop-based PV applications, as recently, there are about 6.8MW rooftop based net energy metering project planted at UTHM, a way to support green energy growth under sustainable development goals.

Changing Epidemiology: Outbreak of Monkey Pox

Monkeypox is a viral illness endemic to African countries. 20 May 2022, W.H.O alarmed all countries on the outbreak of the monkeypox virus1. Symptoms include headache fever swollen lymph nodes lethargy and the development of rash. Two types of clades (strains) are found that is central and West African clades. A central clade is more infectious than a western clade. A western clade is self-limiting within 2-3 weeks with a case fatality rate of 1% while the central clade is a 10% fatality rate. Monkeypox virus causes monkeypox a zoonotic disease which belongs to the poxviridae family2 which is closely related to the smallpox virus. Indicated from historical data smallpox vaccination with vaccinia virus (orthopoxviral) was 85% protective against monkey pox3. Danish laboratory in 1958 discover the virus in monkeys from where its name monkey pox originates4. The first case was discovered in a 9-month baby for the first time in Congo in 19705. A previous systematic review of the summer of 2018 described the epidemiological outbreak of the monkeypox virus6. United Kingdom’s first case was presented on 16 May 24, 2022, after laboratory confirmation7. The incubation period of monkeypox ranges from 6-13 days with possible extension to 5-21 days. The illness consistently ends by 2-4 weeks. Smallpox vaccines provide adequate protection against the monkeypox virus. World health organization suggests that health workers who are treating or exposed to monkeypox patients or their laboratory samples be immunized against smallpox. Effective laboratory investigation is a significant measure for identification and management. PCR on multiple lesions from various sites can be utilized to diagnose the potential condition. It should be sent to the government public lab and the control & command center must be notified. Refrigerated (2-8c) samples should be sent within 5 days of collection. Sample of swab should be of nylon, polyester, or Dacron swab with plastic, wood, or thin aluminum shaft. International support for increased surveillance and detection is important for monkeypox cases for understanding the changing epidemiology of the resurging disease. In the current environment of pandemic threats, the public health importance should not be underestimated. Outside of African countries appearances of cases highlights the risk of geographical spread. Discontinuation of the smallpox vaccine has created a landscape for monkeypox. Government guidelines for emergency diseases should be used with proper notification of case reports to the directorate. Personal protection equipment with equipped labs should be provided. All children less than 12 should be vaccinated with smallpox vaccines. A combination of standard, contact, droplet and airborne precaution should be used. Place the patient in a single room with a portable HEPA filter or airborne infection isolation room. Staff from equipped laboratories should obtain samples from suspected/confirmed monkeypox virus infection. Appropriate personal protective equipment (PPE) should be provided and disposed of properly before leaving the room. Monitoring and tracing contact must be maintained and recorded. World health organization effective hand hygiene five moments should be performed by healthcare workers frequently. Use guidelines for correct containment and disposal of contaminated waste. Be care full always with the soiled laundry to avoid contact with lesion material and used PPE materials. Ensure procedures are in place for cleaning and disinfecting environmental surfaces in patient care zones. Always use the government of Pakistan’s national health guidelines for emergencies.

Effect of soil saturation on load transfer in a pile excited by pure vertical vibration

A comparison between the resistance capacity of a single pile excited by two opposite rotary machines embedded in dry and saturated sandy soil was considered experimentally. A small-scale physical model was manufactured to accomplish the experimental work in the laboratory. The physical model consists of: two small motors supplied with eccentric mass 0·012 kg and eccentric distance 20 mm representing the two opposite rotary machines, an aluminum shaft with 20 mm in diameter as the pile, and a steel plate with dimensions of (160 × 160 × 20 mm) as a pile cap. The experimental work was achieved taking the following parameters into consideration, pile embedment depth ratio (L/d; length to diameter) and operating frequency of the rotary machines. Twenty four tests were conducted in medium dense fine sandy soil with 60% relative density. The results revealed that in dry soil during machine operation the pile tip load decreased for all (L/d) ratios and operating frequencies due to mobilizing the skin friction resistance. Whereas in saturated soil, for small (L/d) ratio and low operating frequency, the mobilized skin friction was affected by the presence of water, which works as a lubricant leading to increase the pile tip load.

Dynamical Investigation of Cam-Follower Profile Under Space - 100 to + 120°C Temperature Condition

Cam-follower mechanism efficiency in production of desired motions has been proved along the history of space missions. In this paper, according to pre-specified spatial condition of wide temperature variations between -100 and +120 Celsius degrees, some new and innovative cam-follower profile designs are presented. In the first follower mechanism, through rotating a connected screw to a servomotor, changes in length of the moving follower on cam is compensated with respect to the temperature changes of certain spatial conditions. In the second design, an inclined surface cam is equipped with an active controllable follower. As the third suggestion, the design with an inclined cam surface is optimized by investigating the length of the shaft connected to the cam. In the fourth model, a new design is proposed by changing the shaft's material from aluminum to titanium and a modified design is presented. The proposed designs are investigated and compared using the analytical solutions and optimization tools using MATLAB and ANSYS. The purpose of this study was to identify the effect of profile type on the dynamic behavior of the mechanism under the effects of a temperature difference of -100 to +120°C in space condition. It is concluded that changing the length of the follower, using an inclined cam surface and optimizing the length of the shaft connected to the follower are all effective solutions to the cam's volume variation problem. The results also indicate that for solving the problem of the volume variation of the cam-follower mechanism a combination of the proposed designs is optimal. Moreover, among the presented designs, the mechanism with an inclined cam surface with an aluminum shaft is shown to have the highest precision and performance with respect to the other three.

Development of novel finishing tool into Magnetic Abrasive Finishing process of Aluminum 6061

ABSTRACT Magnetic Abrasive Finishing (MAF) process is an advanced finishing method involving a dry medium comprising iron and non-magnetic abrasive particles. When this mixture is brought in the magnetic field, it forms a very fine, multiple, and flexible abrasive brushes, which can be used for finishing the magnetic as well as non-magnetic materials such as aluminum. For performing finishing operation on aluminum shaft, novel finishing tool having the fixtures for holding the workpiece and other comprising part have been designed, developed and fabricated. These fixtures are attached to a Lathe machine and moved along the length of the rotating workpiece. The non-magnetic material, which is chosen as aluminum, and the finishing operation is performed on it. Minimum surface roughness 96 nm after the actual surface finish of 400 nm with the change in percentage Ra 76% is achieved using the novel finishing tool.

Ultra-High-Speed Variable Reluctance Motor (Vrm) Applied on Gravimetric Calibration Device With Magnetic Suspension

Variable Reluctance Motors (VRM) have great advantages for applications in the most diverse areas of the industry and equipment, due to its versatility, robustness, stability and the possibility of precise control of rotation, power and torque. In view of these advantages, it was decided to develop and simulate this type of motor for the on-screen prototype, which is intended for the calibration of gravimeters, intended for the detection of gravitational waves through the effect of these waves on rotating objects in ultra-high rotations of the order of 500,000 rpm. The proposed device requires a 1: 10,000 rpm error control, which will be possible due to the stability characteristics of the MRV. Due to the extremely low permissible vibration, the system uses magnetic bearings of the Lenz type in the rotor, with neodymium magnets interacting with the aluminum shaft, ensuring low friction and vibration. All of these aspects can be simulated using Matlab/Simulink, allowing a MRV performance perspective on the prototype.

Study of timbral influence of mallets on the steelpan through spectral analysis

The steelpan is an instrument with unique acoustic properties that allow for a wide range of timbral possibilities influenced by the choice of actuator. It is increasingly common for composers and performers to experiment with mallets made from a variety of materials that produce highly differentiated timbres. Examples of mallet types include wood and aluminum shafts covered with rubber tips, chopsticks, dowel rods, and cardboard tubes. Understanding how mallets interact with the steelpan is an important aspect of performance practice. Aside from standard rubber tipped mallets, most other mallets types are homemade and these characterizations will inform mallet design and construction in order to achieve the desired timbral result. While there have been studies analyzing the modes of vibrations of steelpan notes, the interactions between mallets and timbre hasn’t yet been studied and characterized. The goal of this work is to measure and characterize the timbral influence of a wide variety of mallets on high voiced steelpans through low level audio analysis with a focus on spectral features. Audio recordings were made with more than a dozen different mallets and several steelpans of three different types: tenor, double seconds, and double tenors.

A simple torque magnetometer for magnetic moment measurement of large samples: Application to permanent magnets and bulk superconductors.

The development of large size magnetic materials requires nondestructive measurement techniques to characterize their magnetic moment. In this work, we report the design and construction of a torque magnetometer able to accommodate sizable magnetic samples (>1 cm3) both at room temperature and cryogenic temperature. This device has an intermediate sensitivity between miniature torque magnetometers designed to work at cryogenic temperature and industrial torquemeters poorly adapted to extreme conditions. We show that torque sensing in the range 10-3-100 Nm can be achieved with piezoresistive metallic strain gages cemented on a cylindrical aluminum shaft with external temperature control. An absolute calibration of the device, carried out with a coil fed by a DC current, shows that magnetic moments down to 5 × 10-3 A m2 can be measured by this technique. The magnetometer is used to characterize a Nd-Fe-B permanent magnet and a permanently magnetized bulk, large grain superconductor at liquid nitrogen temperature (77 K). Results are in excellent agreement with data obtained with a flux extraction magnetometer for large samples. The device is able to measure magnetic moments in excess of 1.5 A m2, i.e., two orders of magnitude above the maximum magnetic moment of commercial magnetometers. The sample can be inserted in the air-gap of an electromagnet to measure the decrease in magnetic moment in the presence of a transverse applied field. The device was used to characterize the magnetic moment of "quasibulk" superconductors made of stacked coated conductor tapes (12 mm width) in such "crossed field" conditions.

Aspects of an automatic system of implants of radioac-tive seeds and anatomic object simulator for tests in prostate brachytherapy.

This work presents the development of an automatic radioactive seed implantation system (PSIS). PSIS may assist the testing permanent implants procedure in the prostate. These tests will be important in measurements of absorbed doses in the pelvic structures, involving the organs and tissues at risk to improve planning, seed positioning and dosimetry. The automated Prostate Seed Implant System (PSIS) has been designed to meet operational needs, which offers the freedom when positioning the brachytherapy needle inside the treatment area ensuring repeatability and fidelity to the planned treatment. Both the ultrasound probe and the seed implant needle are driven by stepper motors, ATMEGA microcontroller, bearings, aluminum shafts and a GUI (Graphical User Interface). Movement of both the probe and the needle holder was performed by fixed spindle on a threaded rod going through a stepper motors by a coupling. These engines were chosen due to the necessity of movements precision that these types of motors provide. The project was developed and the PSIS prototype was assembled. The prototype presented acceptable operating characteristics for prostate implants. The advantage of this system is that the automation of the application provides an accurate positioning and movement of both probe and seed application. In addition to this study, seeds implantation tests will be performed, and such tests will be essential in protocol validation processes.

Finite Element Simulation of the Presta Joining Process for Assembled Camshafts: Application to Aluminum Shafts

This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the joining of the cam onto the shaft. When manufactured, the connection is tested randomly by loading it with a static torque. Subsequently, there are three numerical models using the finite element method. Additionally, a material model of finite strain viscoplasticity with nonlinear kinematic hardening is used throughout the whole simulation process, which allows a realistic representation of the material behavior even for large deformations. In addition, it enables a transfer of the deformation history and of the internal stresses between different submodels. This work also shows the required parameter identification and the associated material tests. After comparing the numerical results with experimental studies of the manufacturing process for steel-steel connections, the models are used to extend the joining process to the utilization of aluminum shafts.

Vibration responses of parallel misalignment in Al shaft rotor bearing system with rigid coupling

Preceded by unbalance, misalignment is the second major mechanical fault in rotating machine applications. In spite of using modern alignment techniques like laser alignment tool, the accidental misalignment arises over a period of continuous operation due to many reasons. This can lead to excessive forces on components of rotating systems, which ultimately greatly influence on its vibration spectrum. The study presents the results of Harmonic analysis of the Aluminum (Al) shaft rotor bearing system with rigid coupling, under parallel misalignment, using FEA. It show-cases vibration spectrum due to the misalignment. The results are compared with experimental results based on FFT analyzer for different sub critical speeds. Misalignment effect at coupling location is simulated using nodal force vector. The force vector is found using coupling stiffness matrix, derived from geometrical and material properties and instantaneous parallel misalignment between the two coupled shafts. Based on the FEA and experimental results, parallel misalignment in the shaft rotor system can be predicted almost at all speeds by observing 2X characteristics frequency of operating speed. However to diagnose the nature of misalignment, the knowledge of natural frequency of the system plays a crucial role. It facilitates determination of other dominant characteristic frequencies. An FEA approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation of the system with rigid coupling

Vertical vibration capacity of a single pile in dry sand

ABSTRACTIn this study, the dynamic response of pile foundation in dry sandy soil excited by two opposite rotary machines was considered experimentally. A small scale physical model was manufactured to accomplish the experimental work in the laboratory. The physical model consists of two small motors supplied with eccentric mass (0.012 kg) and eccentric distance (20 mm) representing the two opposite rotary machines, an aluminum shaft as the pile, and a steel plate a pile cap. The experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (L/d, where L is the pile length and d is its diameter) and operating frequency of the rotary machines. All tests were conducted in medium dense fine sandy soil with 60% relative density. Twelve tests were performed to measure the change in load transferred through the pile’s tip to the underlying soil. To predict precisely the dynamic load that will be induced from the rotary machines, a mini load cell with a capacity of 100 kg was mounted between the aluminum plate (the machine base) and the steel plate (pile cap). The results revealed that, before machine operation, the pile tip load was approximately equal to the static load (machine and pile cap), whereas during machines’ operation, the pile tip load decreased for all embedment depth ratios and operating frequencies. This reduction was due to the action of skin friction that was mobilized along the pile during operation, and as a result the factor of safety against pile bearing failure increases. For all operating frequencies and pile lengths, the factor of safety against bearing failure increased during machines’ operation, where the pile tip load became less than its value before starting operation. During operation, the skin friction resistance mobilized along pile length led to decrease the bearing load.

A Joining Method of Shaft and Holed Part Using Plastic Deformation

Abstract A joining method for shaft part and holed part using plastic deformation was proposed. In this method, the shaft having lower deformation resistance is extruded into the holed part with having higher deformation resistance. The wall of the hole had inclination angles along the axial direction. For the verification, the holed part of S45C (in JIS) with uniform internal diameter and various average roughness’s ranging from around 1 to 11 micrometers by lathe turning process were first joined to the outer surface of an A1200 (in JIS) aluminum shaft part. The flat punch was used here. As a result, the material of shaft was adequately fulfilled in the inner surface of the pipe. Second, the joining of the holed part of S45C with inclination angle and the shaft of A1200 was investigated. The punch with the flat head and four different impressions was used here. As a result, the thinner end of the holed part was curled inward and intruded into the shaft material as the extrusion proceeded. The good coincide of the extrusion load for joining between in experiment and calculation by FEM was obtained. Furthermore, the deformation behavior of the holed part was successfully reproduced by the calculation. The joining efficiency by the proposed method was around 69% at maximum for the tensile strength of A1200.

Development of Excess Pore Water Pressure around Piles Excited by Pure Vertical Vibration

In this study, an assessment to excess pore water pressure generated around a single pile and pile group excited by two opposite rotary machines embedded in saturated sandy soil was considered experimentally. A small-scale physical model was manufactured to accomplish the experimental work in the laboratory. The physical model consists of: two small motors supplied with eccentric mass of 0.012 kg and eccentric distance (20 mm) representing the two opposite rotary machines, an aluminum shaft 20 mm in diameter as the pile, and a steel plate with dimensions of (160 × 160 × 20 mm) as a pile cap. The experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (L/d), spacing between piles (S) and operating frequency of the rotary machines. Twelve tests were conducted in medium dense fine sandy soil with 60 % relative density. In all these tests, the change in excess pore water pressure was measured around the pile at two spots: at the middle of the pile and at its tip. The results revealed that the generation of excess pore water pressure was affected by the following parameters: slenderness ratio of the pile, operating frequency of the machines, and the soil permeability. However, for all cases, it was found that the pore water pressure generated during operation was not greater than 20 % of the initial hydrostatic pressure. Using pile foundation reduced the amplitude of vertical vibration by about (300 %) for all operating frequencies, lengths of piles, pile spacings and number of piles. In addition, the presence of piles reduced the disturbance (fluctuation) in this amplitude by about (400 %). For single pile, and under the same operating frequency, a small decrease in the amplitude of vertical vibration resulted from increasing the length of the pile.

Whole diamond stylus for the long play phonograph

Diamond styluses have long been used for long play (LP) phonographs, and remain favored by fans because of their higher fidelity to original sounds compared with compact disk (CD) digital media. In this paper, we report the fabrication and characterizations of a whole diamond stylus integrating the shaft and tip using a large single crystal diamond plate by sophisticated laser machining. This is the first moving magnet (MM) type LP cartridge comprising a whole diamond including the tip and cantilever. According to the frequency response measurements, whole diamond stylus has a lower crosstalk than the conventional stylus; that is, a far larger separation of the right and left channels e.g., 36dB @1kHz. For the 3rd harmonic distortion, which is the most important factor affecting the audio noise characteristics, the whole diamond stylus exhibits significant improvements compared with the conventional aluminum shaft cantilever; a 4dB improvement is observed in the frequency range of 500–800Hz, and a 3–5dB improvement is observed in the frequency range of 1300–1700Hz. Further improvements are expected to yield a well- designed cone-shaped tip over a wide range of frequencies including >20kHz, which was recently identified as the “audible” range for human.

Video-Guided Tube Thoracostomy With Use of an Electrical Nonfiberoptic Endoscope

Tube thoracostomy is a common and generally safe procedure. However, potential hazards can occur during placement of the chest tube. Inasmuch as unexpected injuries may arise from tube thoracostomy, we propose a novel video-guided method. We used an independent complementary metal oxide semiconductor image sensor with a processing chip to obtain a front view image of the chest cavity. The device is connected to an aluminum shaft with four small light-emitting diode crystals in the tip, and a detachable small monitor with a battery inside. The apparatus is small and can be used to direct vision-guided tools in tube thoracostomy. We performed video-guided tube thoracostomy in 6 patients with pleural adhesions. All patients experienced good tolerance to the procedure and had no immediate adverse events. The thoracostomies were performed by a single surgeon with good acceptability, and each procedure was completed in less than 10 minutes. In some cases of pleural adhesion, the video-guided thoracostomy may be a safer alternative to non-image guided tube thoracostomy.

Neural Electrode Array Based on Aluminum: Fabrication and Characterization

A unique neural electrode design is proposed with 3 mm long shafts made from an aluminum-based substrate. The electrode is composed by 100 individualized shafts in a 10 × 10 matrix, in which each aluminum shafts are precisely machined via dicing-saw cutting programs. The result is a bulk structure of aluminum with 65 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> angle sharp tips. Each electrode tip is covered by an iridium oxide thin film layer (ionic transducer) via pulsed sputtering, that provides a stable and a reversible behavior for recording/stimulation purposes, a 40 mC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> charge capacity and a 145 Ω impedance in a wide frequency range of interest (10 Hz-100 kHz). Because of the non-biocompatibility issue that characterizes aluminum, an anodization process is performed that forms an aluminum oxide layer around the aluminum substrate. The result is a passivation layer fully biocompatible that furthermore, enhances the mechanical properties by increasing the robustness of the electrode. For a successful electrode insertion, a 1.1 N load is required. The resultant electrode is a feasible alternative to silicon-based electrode solutions, avoiding the complexity of its fabrication methods and limitations, and increasing the electrode performance.

Experimental Shear Stress Analysis of the Thin Walled Aluminum Hollow Shaft under Torsion

In this experimental study, maximum torsion shear stresses occurring on the hallow aluminum shaft under various small torsion loads were measured with strain gauge, data acquisition cards and computer. Special software was developed to measure maximum strain and stress on the thin aluminum hollow shaft. Stress values occurring on the aluminum hallow shaft under various small loads were measured with strain gauge and those strain values were transmitted to computer directly with data acquisition cards. Using the strain, the load and other constant values of the material (Torsion stress, outside and inside diameters of shaft, length of shaft, shear stress modulus, applied torque loads, twist angle of shaft etc) the stress values occurring on the hallow shaft are calculated by computer program and the stress-strain graph is drawn on the computer screen automatically [Refer to table1 Fig. 2,3,4 ,5 and . In this experimental study, the theoretical knowledge given in the books and experiment results obtained under laboratory conditions were compared with each other. The obtained results were almost same. Similar experimental application could be used for real applications in car industry and mobile machines [.