41results about How to "Small space restrictions" patented technology

The invention provides an unmanned aerial vehicle monitoring system for monitoring floating objects in water. The system comprises a UAV (unmanned aerial vehicle) cruise module and a ground monitoring processing module. By using the UAV cruise module to carry out monitoring, most water areas can be reached, the implementation difficulty of monitoring is small, a UAV does not carry monitoring personnel, the UAV cruise module reaches an observation point in the air, the disadvantages of power safety reliability and the interference of water area velocity and water flow direction by using an observation ship are overcome, the possibility of accidents is little, the reliability and safety of monitoring are improved, the floating objects in a large water area can be monitored in a short time, the monitoring efficiency is improved, a lot of manpower and resources are saved, the energy consumption of monitoring personnel is reduced, a monitoring area and a water area floating object area can be accurately calculated, the density of the water area floating objects is accurately calculated, and the analysis decision and further measures are facilitated according to provided detailed monitoring data.

The invention discloses a conveying and installation vehicle for a hanging-type full-automatic edge roller. The conveying and installation vehicle comprises an installation platform and a supporting platform, baffles are arranged at two ends of the installation platform respectively, hanging-type edge roller installation holes are formed in the installation platform, a trolley is installed at the bottom end of the supporting platform, a guiding rod is installed between the supporting platform and the end part of the installation platform, a lifting machine is installed in the middle part of the installation platform and the supporting platform, and the lifting machine comprises a lifting rod which is fixedly connected to the bottom end of the installation platform, and a rocker which is rotationally arranged on the supporting platform in a transverse direction. According to the conveying and installation vehicle for the hanging-type full-automatic edge roller, the hanging-type edge roller can be conveniently transported to a designated place and adjusted to a suitable installation position through the conveying and installation vehicle; meanwhile, the conveying and installation vehicle is low in manufacturing cost, convenient to operate, small in volume, convenient to transport; besides, the conveying and installation vehicle suffers little form site limitation, and installation cost is reduced.

The invention relates to the technical field of bridge construction, in particular to a large-scale steel box beam ashore construction method. The large-scale steel box beam ashore construction method comprises the steps that water transportation of steel box beams is carried out, boats are used for carrying out the water transportation on the steel box beams, and the steel box beams are arranged on the decks of the boats through bearing timber piers and air bags; locating devices are set, ground anchors are arranged on a shore, and at least four ground anchors are arranged; a shore connecting dock is constructed, retaining walls are built up, sliding rampways are constructed from the retaining walls towards the shore in a stretching mode, and sliding rails are paved on the sliding rampways; ashore bearing is carrying out on the steel box beams by using the air bags, and the steel box beams are transferred to the shore through the air bags. According to the large-scale steel box beam ashore construction method, the operation of lifting, transferring, going aboard and going ashore on the steel box beams is achieved by adopting the air bags, the application of air bag operation is small in restriction of sites, a lifting function and a moving transporting function are provided, large-scale mechanical equipment is not needed, therefore, project cycles can be shortened, and a great amount of capital can be saved.

The invention discloses a confidential propaganda education training system based on virtual reality and an implementation method thereof. A multi-scene switching relation module is used for controlling switching operation of all scenes in the whole system and guaranteeing the correct sequence of single-scene loading and operation. A single-scene operation mechanism module is used for realizing independent operation of a single virtual scene; the multi-scene switching relation module needs to ensure that the next single scene in sequence is in a locked state, and only after the task of the current single scene is completed, the next single scene can be triggered to be unlocked; in addition, what needs to be guaranteed is that in the process that the user receives confidential propaganda education based on virtual reality, immersion interaction experience is completed on the current single scene through the man-machine interaction module. The scene required by the content is displayed in the VR helmet through the virtual reality technology, so that the user interacts with the virtual scene through the handle, and the sense of reality and immersion of the crime scene in the secret-related case are realized.

The invention provides a novel-configuration tilt rotor aircraft and a flight control method thereof. According to the aircraft, a conventional vertical fin and horizontal fin are arranged at the tailof an aircraft body, and two sets of wings are arranged on the two sides of the middle of the aircraft body. Each wing comprises an inner-section wing and an outer-section wing which are connected through a folding mechanism, and a set of foldable rotors is arranged at the tail end of each outer-section wing; and the outer-section wings can simultaneously finish two actions of folding and rotating around the inner-section wings through the folding mechanisms. When the aircraft vertically takes off and lands, the obstruction of wings to the downwash flow of the rotor wings can be reduced; on the other hand, the body size and the projection area can be reduced. When the aircraft flies in the air, the wings are unfolded, the rotor wings are folded, resistance brought by the rotor wings during high-speed forward flight can be effectively reduced, and therefore the forward flight speed is increased.

The invention discloses a combined cable hoisting and laying auxiliary device, which comprises a horizontal fixing component, a side fixing component, a steel cable fixing cross arm and an anti-sway fixing bracket, wherein the horizontal fixing component and the side fixing component are assembled into a trapezoidal structural frame; the anti-sway fixing bracket is fixed to the upper part of the trapezoidal structural frame and is located at one side of the side fixing component for fixing and hoisting a fixed pulley; the steel cable fixing cross arm is fixed to the top of the trapezoidal structural frame and located above the anti-sway fixing bracket for hoisting a steel cable. The combined cable hoisting and laying auxiliary device does not need the help of a ceiling structure as a fixing point, and eliminates the damage influence on a building. The hoisting frame is stable and reliable in design, can avoid hidden dangers such as collapse and the like, is not restricted by the sites,is fixed by a lateral fixing part, and is suitable for all installation sites. Regardless of a narrow cable well or an equipment-intensive equipment room, the hoisting frame is detachable and reusable, thereby reducing construction and installation cost. The combined cable hoisting and laying auxiliary device can be widely used.

The invention relates to the technical field of metal thickness measurement and discloses a hole-surface copper integrated thickness measuring device and a thickness measuring method for five-terminalmeasurement of micro resistance. The thickness measuring device mainly comprises two clamps which are symmetrically arranged in an up-down mode. The clamp further comprises two air cylinders, a mounting plate for mounting the air cylinders, a protection flat plate and a five-terminal thickness measuring probe. The thickness measuring method comprises the steps that the five-terminal thickness measuring probes of the two clamps are moved to a measuring position, four probe pins on the five-terminal thickness measuring probes are used for measuring the thickness of an upper copper layer and a lower copper layer, a hole wall copper thickness measuring assembly is used for measuring the voltage of a hole wall copper layer in an up-and-down combined mode, and then the resistance is calculated.The thickness of the hole wall copper layer is calculated according to the diameter, height and resistance of the hole wall copper layer and the thickness of the upper copper layer and the lower copper layer. According to the device and the method in the invention, two kinds of hole copper parameters can be measured at the same time in one device, and the measurement process is simplified.

The present invention discloses a roller type Chinese prickly ash seed and shell separation mechanism. The roller type Chinese prickly ash seed and shell separation mechanism comprises a material storage hopper, a shaft-free screw conveyor, a shelling chamber, a screening box and a screen; the material storage hopper is arranged on a machine frame; the top part of the screening box is provided with a shelling chamber used for shelling Chinese prickly ash; the bottom part of the material storage hopper feeds materials to the shelling chamber via the inclinedly arranged shaft-free screw conveyor; the end part of the shaft-free screw conveyor is provided with a material outlet; the material outlet is connected with the shelling chamber; and the inside of the shelling chamber is provided withan upper shelling roller, a left shelling roller and a right shelling roller. Beneficial effects are as follows: the shaft-free screw conveyor is simple in operation, convenient to install, and less restricted by sites; at the same time, due to a side pressure provided by the upper shelling roller, the left shelling roller and the right shelling roller can better achieve the shelling effects.

The invention discloses a comfortable energy-saving artificial tree house which comprises a house main body, a stairway and bearing steel tubes for supporting the house main body, wherein the house main body comprises a frame, a wall body and a floor; the frame is of a steel structure; the wall body comprises an inner wall body, an outer wall body and a cavity in the wall; the inner wall body is arranged inside the frame, the outer wall body is arranged outside the frame, and the cavity in the wall is positioned between the inner wall body and the outer wall body and is filled with insulating rock wool; the floor is laid on the bottom frame; the outer surface of the wall body is stacked and covered with tiles; a door and a window are formed in the side face of the house main body; and a skylight is formed in the top of the house main body. The comfortable energy-saving artificial tree house is capable of reducing the site limitation to tree house construction, improving the construction efficiency and reducing the energy consumption, and is more comfortable and attractive.

The invention relates to a multi-working-condition simulation combination device for foundation pile low strain detection, which comprises a cylindrical simulation pile, a shading bag is sleeved outside the simulation pile, the simulation pile comprises at least one first pile body, the head end of the first pile body is provided with a first threaded column, and the tail end of the first pile body is provided with a first screw hole matched with the first threaded column; the simulation pile further comprises a male end socket and a female end socket, the male end socket comprises a cylindrical first column body, and a second threaded column matched with the first screw hole is arranged at the head end of the first column body; and the female end socket is a cylindrical second cylinder, and the tail end of the second cylinder is provided with a second screw hole matched with the first threaded column. The multi-working-condition simulation combination device for foundation pile low strain detection is small in occupied area, easy and convenient to mount and dismount, low in cost and small in site limitation; and after random combination, the simulated defect sample size is large,and the implementation effect is good.

The invention discloses an immersive extension stage system based on aerial imaging, and belongs to the technical field of three-dimensional imaging technologies. The immersive extension stage systemcomprises a projection array arranged in a stage and used for projecting images, a scattering assembly used for diffusing the images in multiple directions, a plurality of intelligent light-emitting devices capable of flying and creating images, and a control terminal; the control terminal is connected with a control system; the projection array is connected with a projection management system; all the intelligent light-emitting devices are connected with a light-emitting device management system, and the control system comprises an information input module, a route planning module, a storagemodule, a projection sending module and a light-emitting device sending module; the projection management system comprises a projection receiving module and a projection control module; and the light-emitting device management system comprises a light-emitting device receiving module, a positioning module and a light-emitting device control module. The immersive extension stage system has the effects that the virtual images and the physical stereoscopic images are simultaneously generated to form the virtuality and reality combined visionary sense, and influences by the space and lamp light are small.

The invention relates to the technical field of fitness ball games, and discloses court equipment of a fitness ball game ground volleyball. The court equipment comprises a net, a main court, an outer court and a non-barrier area, wherein the main court is arranged as a rectangle and positioned at the center of the outer court at the center of the non-barrier area; the net arranged in the middle of the main court divides the main court into main court areas for two parties; the main court areas comprise quick attack areas, strong attack areas and back court areas; the areas in the middle of the two sides of the net are the quick attack areas, and the two sides are non-attack areas; the sides of the quick attack areas which are far away from the quick attack areas are the strong attack areas and the back court areas; and the service areas which are arranged outside of the end lines of the back court areas are positioned in the middles outside of the end lines of the back court areas. The court disclosed in the invention is large in activity area, multiple in attack and defense variation, adjustable in amount of exercise, and small in court limitation; and the used integral net has the characteristics of high elasticity, double-sided property of the upper edge, various over-net changes, integration, ornamental value, interestingness and portable structure, and is suitable for competition exercise of the fitness ball game ground volleyball.

The invention discloses a solid-liquid separation device and application thereof.The solid-liquid separation device comprises a main body which is a cylindrical cavity.A stirring flow pushing apparatus is mounted on the top of the cylindrical cavity, and a turbulent flow paddle or a flow pushing pump of the stirring flow pushing apparatus extend into the cylindrical cavity; a sewage inlet is formed in a side wall of the upper portion of the cylindrical cavity, and mud discharge outlets are formed in the side walls of the lower portion of the cylindrical cavity or the bottom of the cylindrical cavity; a partition plate is arranged inside the cylindrical cavity, a relatively closed conical cavity is enclosed by the partition plate in the cylindrical cavity, and the bottom of the conical cavity is communicated with the cylindrical cavity; a clear water overflow port is arranged on the top of the conical cavity.The solid-liquid separation device and the application have the advantages that the partition plate is arranged in the cylindrical cavity, the conical cavity is enclosed by the partition plate, accordingly, quick mixing regions, slow mixing regions and sludge concentrating and settling regions can be formed, functions of coagulating basins and settling basins can be integrated with one another, the solid-liquid separation device is small in occupied area, low in cost, repair and maintenance cost and failure occurrence rate and easy to operate, and only few facilities are required; the solid-liquid separation speeds can be effectively increased under double effects of centrifugal force and gravitational force, and solid-liquid separation effects can be effectively improved under the double effects of the centrifugal force and the gravitational force; excellent foundation can be laid for popularizing sewage purification environmental protection equipment.

The invention discloses a boresighting data acquisition system and an aircraft gun boresighting method. The boresighting data acquisition system can be used for acquiring rolling angle data, pitchingangle data and yaw angle data; and a boresighting lens has no need to be manually adjusted during the whole data acquiring and debugging process, and whether the boresighting lens aims at a target plate or not has no need to be judged manually during the process of enabling the boresighting lens to aim at the target plate far away from an aircraft gun, so that human intervention during the boresighting data acquisition process is reduced, the personal error during the aircraft gun boresighting process is reduced, and the measuring accuracy and the boresighting efficiency of aircraft gun boresighting are improved. In addition, the practical application discovers that a horizontal distance between a second data acquisition module and a first data acquisition module of the boresighting data acquisition system is one fifth of a horizontal distance between the boresighting lens and the target plate in the prior art, so that the site limitation on acquiring boresighting data by utilizing theboresighting data acquisition system is greatly reduced.

The invention relates to a VR interactive teaching device based on virtual disassembly and assembly detection of a high-voltage part of a pure electric vehicle. The device comprises a learning and operation module which is used for importing part information and determining an optimal disassembly and assembly sequence; a guidance module which is used for building a virtual disassembly and assembly teaching platform; and an evaluation module which is used for constructing an evaluation system, monitoring the operation state of the trainee and comprehensively evaluating the trainee. By constructing the 3D interactive teaching system for high-voltage part detection and related part understanding practical training projects of the new energy automobile, a teacher issues VR teaching resources through a PC terminal, updates task content in time on a VR software platform and guides teaching, and students can carry out interactive learning training through VR equipment, so that the learning interest of the students can be improved, repeated practice can be realized, the operation process is well-recognized and standardized, and a guarantee is provided for safe practical training operation. The problem of large potential safety hazard of classroom practical training teaching of traditional new energy technology courses is solved.

The invention discloses an infant early education robot capable of achieving projection. The infant early education robot capable of achieving projection comprises a fixed base and a hollow shell, the hollow shell is arranged on the fixed base, a storage battery, a processing controller and a storage device are arranged in the hollow shell, the storage battery and the storage device are connected with the processing controller, a man-machine interaction module connected with the processing controller is arranged on the hollow shell, a projection instrument is arranged above the man-machine interaction module, and is connected with the processing controller, and a wireless signal transmission module is arranged on the projection instrument and is connected with the processing controller; through the above manner, according to the infant early education robot capable of achieving projection., the projection instrument can be used for enlarging the display area, the infant can conveniently perform learning, the side effect on eye development is avoided, moving is flexible, the angular adjustment is convenient, the site limit is small, communication between parents and the infant is convenient, and education of the infant is improved.

The invention discloses a new energy automobile power battery self-adaptive transshipment device which comprises a movable frame, a lifting bracket assembly, a transshipment clamping table and a positioning supporting table, the lifting bracket assembly is fixedly installed on the surface of the movable frame, and the lifting bracket assembly comprises a lifting guide frame, a moving arm, a bracket deflection steering wheel and a deflection steering engine; a lifting frame is slidably mounted on the inner side of the lifting guide frame, and the bracket deflection steering wheel is fixedly mounted at the top end of the lifting frame. According to the transport vehicle, by arranging an automatic guide type vehicle body structure and utilizing electromagnetic or optical or radar laser automatic guide mechanisms of equipment, the transport vehicle can run along a specified guide path, has safety protection and various transfer functions, and is provided with a trolley programming device, a parking selection device, safety protection and various transfer functions; and under the monitoring of a computer, the self-adaptive transshipment robot can be autonomously driven in an unmanned manner according to an instruction, automatically runs along a specified guide path and arrives at a specified place, so that a self-adaptive transshipment task is completed.

The invention discloses a high-efficiency solid-liquid separation device and an application thereof. A main body of the solid-liquid separation device is a cylindrical cavity, the inner side wall of the cylindrical cavity is provided with a threaded channel extending downwards, the top of the cylindrical cavity is provided with a stirring water impeller, and a flow disturbance paddle or water impelling pump of the stirring water impeller extends into the cylindrical cavity; the side wall of the upper part of the cylindrical cavity is provided with a sewage inlet, the side wall of the lower part or the bottom of the cylindrical cavity is provided with a sludge discharge port; the cylindrical cavity is internally provided with separation plates; a relatively closed conical cavity is enclosed by the separation plates enclose, and the bottom of the conical cavity communicates with the cylindrical cavity; the top of the conical cavity is provided with a clear water overflow port. The conical cavity is enclosed by the separation plates, and a fast mixing region, a slow mixing region and a sludge concentration and precipitation region are formed, so as to realize function integration of a coagulation tank and a sedimentation tank; the device has the advantages of small land occupation, less required equipment, low cost, low maintenance costs, simple operation, and low failure generation rate. By using double action of centrifugal force and gravity, and under the guidance of the threaded channel, the speed and the effect of solid-liquid separation are improved.

The present invention relates to a production technology of cellared chopped capsicum frutescens. Picked fresh capsicum frutescens in the same day is washed clean; bases are removed; the capsicum frutescens is drained; the drained capsicum frutescens is chopped for a standby application; according to the parts by weight, 100 parts of the capsicum frutescens, 12-15 parts of edible salt and 1 part of baijiu are mixed in the ratio; even mixing and stirring are conducted; the stirred raw materials are loaded in a multi-cavity ceramic jar; the multi-chamber ceramic jar is buried under ground at a constant temperature of 20-25 DEG C; a material inlet is only left outside; after pickling, the ceramic jar is taken out; and the capsicum frutescens is sub-packaged into bottles and barrels. The special multi-cavity ceramic jar is used; constant-temperature soil cellaring pickling is conducted; and the pickled chopped capsicum frutescens is unique in flavor, higher in crispness and chroma, and also energy-saving and environmentally protective.

The invention discloses a swivel construction method for a bridge in a water-rich area. The swivel construction method comprises the steps of firstly, installing a temporary water stop structure of a swivel spherical hinge support; 2, constructing a spherical hinge mounting bearing platform; 3, hoisting the swivel spherical hinge support; 4, adjusting the horizontal position of the swivel spherical hinge support; 5, fixing the swivel spherical hinge support; 6, constructing a rotator the bridge body structure; and 7, locking the swivel spherical hinge support and mounting the permanent water stop structure of the swivel spherical hinge support. The horizontal position of the swivel spherical hinge support is adjusted in three directions by arranging the jack, the occupied space is small, height positioning of the swivel spherical hinge support can be achieved only through one-time hoisting, the positioning and mounting speed of the swivel spherical hinge support is greatly increased, and meanwhile, water stop sealing structures are installed on the swivel spherical hinge support before and after swivel of the swivel beam, it is guaranteed that impurities can be prevented from entering the swivel spherical hinge support in the process that the swivel spherical hinge support waits for swivel, and therefore the swivel effect during swivel construction is guaranteed, and application and popularization are facilitated.

A construction method for a weak surrounding rock tunnel inverted arch long anchor rod comprises the steps of construction preparation, steel pipe (2) embedding, long anchor rod (1) manufacturing, staking out in survey, steel pipe embedding, long anchor rod manufacturing and anchor sealing. The engineering cost is reduced, the inverted arch closing time is shortened, the construction progress is accelerated, and construction organization of all parts and all procedures is facilitated.

The invention relates to the technical field of fitness ball games, and discloses court equipment of a fitness ball game ground volleyball. The court equipment comprises a net, a main court, an outer court and a non-barrier area, wherein the main court is arranged as a rectangle and positioned at the center of the outer court at the center of the non-barrier area; the net arranged in the middle of the main court divides the main court into main court areas for two parties; the main court areas comprise quick attack areas, strong attack areas and back court areas; the areas in the middle of the two sides of the net are the quick attack areas, and the two sides are non-attack areas; the sides of the quick attack areas which are far away from the quick attack areas are the strong attack areas and the back court areas; and the service areas which are arranged outside of the end lines of the back court areas are positioned in the middles outside of the end lines of the back court areas. The court disclosed in the invention is large in activity area, multiple in attack and defense variation, adjustable in amount of exercise, and small in court limitation; and the used integral net has the characteristics of high elasticity, double-sided property of the upper edge, various over-net changes, integration, ornamental value, interestingness and portable structure, and is suitable for competition exercise of the fitness ball game ground volleyball.

The invention relates to the technical field of production equipment, and discloses a plate drying production line. The plate drying production line comprises a circulating dryer, a plate feeding device and a plate discharging device. The circulating dryer comprises a circulating conveying device and a drying oven device arranged on the periphery of the circulating conveying device in a surrounding mode. The circulating conveying device comprises a conveying driving component and a belt plate component used for bearing external materials. The multiple band plate components are arranged and distributed along the closed-loop circulation track, and the conveying driving component is used for driving the band plate components to move along the circulation track. The plate feeding device is used for conveying external materials to the circulating conveying device, and the plate discharging device is used for conveying the materials on the circulating conveying device to the outside of the circulating dryer. According to the plate drying production line, the plates are circularly conveyed in the drying oven device and can enter and exit from the same side of the drying oven device, the space utilization rate is high, heat loss is small, and energy consumption can be effectively reduced. The method can be applied to plate processing and production.

The invention relates to the technical field of production equipment, and discloses a plate drying production line. The board drying production line includes a circulation dryer, a board feeding device, and a board unloading device. The circulation dryer includes a circulation conveying device and an oven device surrounding the periphery of the circulation conveying device. The circular conveying device includes a conveying drive member and a belt plate member for supporting foreign materials. A plurality of belt-plate components are arranged and distributed along a closed-loop circulation track, and the conveying driving component is used to drive the belt-plate components to move along the cycle track. The plate feeding device is used to transport foreign materials to the circulation conveying device, and the plate unloading device is used to transport the materials on the circulating conveying device to the outside of the circulating dryer. In the board drying production line of the present invention, the boards are conveyed circularly in the oven device, can enter and exit on the same side of the oven device, have high space utilization rate, less heat loss, and can effectively reduce energy consumption. The invention can be applied in plate processing production.

The invention discloses an obstacle removing device and an obstacle removing method for deep pipeline obstacle removing. According to the specific implementation mode, the obstacle removing device for deep pipeline obstacle removing comprises a steel jacket box supporting device and is characterized in that the steel jacket box supporting device comprises a steel panel structure and a supporting structure, the steel panel structure comprises front panels and side panels, the side panels are arranged between the front panels, and the front panels and the side panels are welded into a ring shape; and the supporting structure is arranged in the steel jacket box supporting device, and the supporting structure and the front panels are welded and fixed. According to the obstacle removing device, the risk of collapse of a trench of an underground diaphragm wall can be effectively solved, and the safe and stable operation environment in the steel jacket box is ensured; and meanwhile, the obstacle clearing period of a deep pipeline in the construction process of the underground diaphragm wall is shortened, the site limitation of obstacle clearing is reduced, and the economic cost of obstacle clearing is reduced.

The invention discloses an impeller calibration system and a method for calibrating an impeller. The impeller calibration system comprises: a fan used for providing stable air flow; a wind tunnel flowchannel arranged at the downstream of the fan and used for guiding the air flow from the fan; a frequency converter arranged on the wind tunnel flow channel and used for controlling the air flow in the wind tunnel flow channel; a flow meter that is arranged on the wind tunnel flow channel and used for measuring the air flow in the wind tunnel flow channel; a rectifying device arranged in the windtunnel flow channel and used for ensuring the stability and the uniformity of a flow field in the wind tunnel flow channel; a test cabin arranged in the wind tunnel flow channel and used for placinga to-be-tested impeller; a drainage section arranged at the downstream of the test cabin in the wind tunnel flow channel and used for ensuring that the flow field in the test cabin is not interfered;and a data acquisition instrument used for acquiring the frequency of the impeller. According to the impeller calibration system and the method, the impeller can be conveniently calibrated.

The invention belongs to a ground volleyball for fitness ball type sports, a court and equipment, relating to the technical field of fitness ball type sports. The ground volleyball is a ball with big elasticity, soft ball surface and favorable feel and is provided with a ball inner container (1) of which the air pressure is 0.25-0.29 kg / cm; the circumferences of the ball inner container (1) are respectively 0.67-0.68 m, 0.68-0.69 m and 0.69-0.70 m; the ball inner container (1) is provided with an aerated air jet, and the outer wall of the ball inner container (1) is provided with a soft sheepskin ball case stuck by binder; and the weights of the balls are respectively 210-230g and 230-250g. The invention has the advantages of low ball speed, more over-net variation, strong appreciation and high enjoyment.