71results about How to "Reduce accident rate" patented technology

The invention provides a traffic participant road condition early warning method and system based on a smart phone, and relates to the technical field of active safety. The method comprises the following steps: acquiring a video stream through a smart phone camera, and synchronously acquiring data of a gyroscope, an accelerometer, an ambient light sensor and a GPS; identifying a user motion state and an environment scene based on the sensor data; carrying out target detection, semantic segmentation and distance estimation on the video frame by adopting a lightweight neural network; performing risk assessment according to the target type, the distance and the movement speed of the user, and generating an early warning instruction; a multi-mode warning is sent to a user in a voice, vibration, vision or interface switching mode; and dynamically adjusting the analysis frequency and the power consumption mode according to the environmental complexity. Existing hardware of the smart phone is fully utilized, extra equipment is not needed, low-cost and high-universality real-time environment perception and active early warning are achieved, and the travel safety of traffic participants such as walking and riding is remarkably improved.

The application provides a fixed installation tray and system for electric resistance measurement of an electric igniter, a plurality of parallelly arranged electric igniter installation slots are arranged in the tray body, a plurality of parallelly arranged wire installation slots are arranged in the tray body, and two wire installation slots are arranged corresponding to each electric igniter installation slot; an electric igniter fixing device is arranged in each electric igniter installation slot, and a wire fixing device is arranged in each wire installation slot. The fixed installation tray has a reasonable overall structure, can conveniently and stably fix the electric igniter to be detected, and can clamp and fix the wire of the electric igniter to be detected, so as to meet the requirement of electric resistance measurement of the electric igniter to be detected. The realization of automatic operation and measurement of the electric resistance of the electric igniter to be detected is facilitated, the accident rate is reduced, and the possibility of personal injury of workers is reduced.

The utility model discloses a kind of semitrailer tarpaulin devices, comprising: semitrailer floor, the top of the semitrailer floor is fixedly connected with vertical plate, the top of the vertical plate is fixedly connected with top plate, the top of the semitrailer floor is fixedly connected with the side of head baffle;Top shielding component, the top of the head baffle is fixedly connected with the side of top shielding component, side shielding component, the side of the vertical plate is fixedly connected with the side of side shielding component, the tail shielding component is used to adopt tarpaulin shielding to the tail of semitrailer, the utility model relates to tarpaulin device technical field.The semitrailer tarpaulin device, by the setting of top shielding component, by driving motor directly driving threaded block drives the rotation axis of far end to move outward, first tarpaulin is spread over the top of entire semitrailer, and first tarpaulin is carried by multiple rotation axes, can evenly share tarpaulin quality, avoid causing equipment overload in moving process.

The application discloses a smart community police management system and method based on Internet of Things security, and belongs to the technical field of smart communities, and solves the problem that existing system data processing cannot utilize edge computing nodes for low-delay real-time analysis, and cannot meet timely early warning requirements, the method comprising preprocessing of multi-source heterogeneous community monitoring information, analysis and processing of the community monitoring information based on edge computing, and generation of a risk propagation path in combination with front-end analysis results and heterogeneity characteristics; in the application, analysis and processing of the community monitoring information based on edge computing avoids the delay of centralized processing, can quickly trigger early warning in the early stage of a risk event, thereby gaining golden disposal time for risk event disposal, and a risk analysis model realizes a leap from single-node anomaly detection to composite risk quantification through multi-dimensional feature fusion and dynamic space-time reasoning, and realizes multi-dimensional feature fusion and dynamic reasoning capability of the risk event.

The invention discloses a bus duct temperature field real-time monitoring and early warning method based on multi-sensor fusion. The method comprises the following steps: step 1, arranging and initializing a multi-type sensor array; 2, collecting and preprocessing data of a multi-source sensor; 3, reconstructing a temperature field based on hierarchical fusion; 4, calculating a dynamic early warning threshold value; 5, temperature field monitoring and grading early warning are carried out; step 6, verification and data updating after early warning; multi-type sensor array three-dimensional arrangement is adopted, a hierarchical fusion algorithm is combined, comprehensive and accurate reconstruction of a bus duct temperature field is achieved, the problems that a single sensor is limited in monitoring range and poor in data reliability are solved, the temperature monitoring precision is improved to be within + / -0.2 DEG C, and a local overheating area can be accurately positioned; the dynamic early warning threshold value is calculated based on the environment temperature and the load current, the defects that a fixed threshold value is prone to false early warning and early warning omission are overcome, and monitoring requirements under different operation working conditions can be met.

The crystal separation system comprises a crystallizing tank, a centrifugal machine and a drying machine which are sequentially connected, the crystallizing tank is connected to a centrifugal machine feeding pipeline of the centrifugal machine through a crystallizing tank discharging pipeline, and the centrifugal machine is provided with a centrifugal machine liquid outlet pipeline connected to a mother liquor tank and further provided with a centrifugal machine discharging pipeline connected to the drying machine. A temperature sensor is installed on the centrifugal machine and used for detecting the temperature in the centrifugal machine, a smoke detector is further arranged above the centrifugal machine, and the temperature sensor and the smoke detector are both connected with a PLC. The internal state of the centrifugal machine can be monitored in real time under the dynamic operation condition of the centrifugal machine, abnormal conditions such as temperature abnormity or smoke concentration abnormity can be found in time, and an alarm is triggered immediately to take emergency measures.

This invention provides a three-trailer collaborative aircraft transfer method and system based on multi-sensor fusion. This invention relates to the field of aircraft ground support technology, specifically to a three-trailer collaborative aircraft transfer method based on multi-sensor fusion, applicable to short-haul aircraft ground transport to hangars. Through multi-sensor data fusion and multi-trailer collaborative control, it improves transfer accuracy, safety, and efficiency. The method specifically includes the following steps: system setup and sensor calibration; trailer attitude initialization and collaborative parameter configuration; real-time acquisition and preprocessing of multi-sensor data; multi-sensor data fusion and state estimation; dynamic path planning based on fused data; attitude error quantification and calibration based on complex statistics; multi-trailer collaborative driving control and traction distribution; real-time environmental monitoring and risk warning; precise docking at the hangar entrance and attitude fine-tuning; and parking and system review and optimization.

The utility model relates to an unstacker control system based on visual analysis, and belongs to the technical field of structural steel unstacking application equipment in the metallurgical industry. According to the technical scheme, the unstacker comprises a steel conveying roller way (1), an unstacker (2) and an unstacker electromagnet (3) and further comprises an inlet light source (6), an inlet camera (7), an outlet light source (8), an outlet camera (9), an inlet camera portal frame (10) and an outlet camera support (11), the inlet camera portal frame (10) is installed at an inlet of the steel conveying roller way (1), and the inlet light source (6) and the inlet camera (7) are fixed to the inlet camera portal frame (10) respectively. An outlet camera support (11) is installed at an inlet and an outlet of the conveying roller way (1), and an outlet light source (8) and an outlet camera (9) are respectively fixed on the outlet camera support (11). The electromagnet magnetism is adjusted through visual analysis, the phenomena of less attraction and more attraction of the electromagnet can be avoided, and automatic operation of the unstacker is achieved.

The utility model discloses a kind of support pressure wheel hangers convenient to install, it is related to mining equipment technical field, including steel column, multiple mounting holes are set on the steel column, and the inside thread connection of mounting hole has installation mechanism, the side fixed connection of installation mechanism has mounting plate, and the inside of mounting plate is rotatably connected with multiple rotating rods respectively, the utility model is rotated clockwise when ratchet wheel is driven by rotating rod, ratchet pawl slides through ratchet wheel tooth groove and allows to rotate;When rotating counterclockwise, ratchet pawl is clamped into tooth groove and prevents reverse, realizes one-way limit, and fixed block always extrudes spring, continuously exerts spring force towards tooth groove to ratchet pawl, ensure that it is closely engaged with ratchet wheel and timely back position clamping;And the fixed column of ratchet pawl one end is rotatably connected with the inner wall of containing frame, ensure that ratchet pawl rotates flexibly, this mechanism can prevent equipment accidental reverse, avoid steel wire rope to slip, improve hoisting and conveying scene operating safety, reduce accident rate.

The utility model relates to the technical field of high-place operation, and discloses an alarm device for a high-place operation hanging basket, which solves the problems in the background technology, and comprises a hanging basket body, the hanging basket body is provided with a hanging bracket, the hanging bracket is connected with a steel wire rope, the hanging basket body is provided with an alarm, and the alarm is connected with the hanging basket body. A weight sensor is arranged at the bottom of the hanging basket body, a tilt angle sensor is arranged at the bottom of the hanging basket body, the hanging basket body is provided with fences, the fences are connected with a hanging support, the fence on one side is provided with an inlet allowing workers to pass through, a support is arranged on the fence on the other side, and an anemograph is arranged on the support. The device has the advantages that the loading state and the balance of the hanging basket can be accurately monitored, the defect that a traditional device can only detect a single parameter is overcome, and the accident rate is reduced.

This application provides an intelligent battery swapping cabinet system with early warning of thermal runaway, relating to the field of new energy technology. It includes a data acquisition and labeling module and a location risk analysis module. If the overall hazard level exceeds a preset threshold, a risk judgment basis is constructed based on the degree of location and quantity impact. A weighted analysis method is used to prioritize the processing of each battery, resulting in an intervention target sequence. Based on the intervention target sequence, combined with the risk propagation range and fault propagation path, an emergency process adjustment plan is dynamically generated. The intervention strategy is iteratively updated through real-time monitoring data to determine the final intervention execution path. This intelligent battery swapping cabinet system with early warning of thermal runaway significantly improves the early warning capability and overall safety and reliability of the swapping cabinet under complex operating conditions, reduces the probability of accidents, and enhances the safety assurance level of new energy battery swapping infrastructure.

The embodiment of the application provides a kind of early warning method and system of energy storage system based on dynamic threshold, belong to safety monitoring technical field.The method includes: the multi-source operating data of energy storage system is collected, and monitoring data set is formed;Feature parameters are extracted based on the monitoring data set, and fusion feature vector is generated based on the extracted feature parameters;According to the fusion feature vector, dynamic threshold determination is executed, and the determined dynamic threshold is obtained;The safety state of the monitoring data set is evaluated based on the dynamic threshold, and the early warning result of energy storage system is output.The application scheme can realize more accurate identification and prompt in the early risk of energy storage system thermal runaway, thereby significantly improve the reliability and adaptability of early warning result, reduce the delay of operation and maintenance intervention and the probability of accident.

The application discloses a thermal state operation whole-process risk prevention and control execution method for intelligent learning of a thermal power plant, and particularly relates to the technical field of safety monitoring of a thermal power plant, and the method comprises the following steps: collecting multi-dimensional thermal state data of equipment, personnel and environment and performing space-time alignment, constructing a space-time synchronous thermal state tensor and a digital twin; calculating the thermal entropy increase rate of equipment and the thermal entropy increase rate of personnel based on the entropy increase principle of non-equilibrium thermodynamics, and constructing a joint entropy increase index to unify and quantify risks; inputting data into a deep reinforcement learning model to predict an operation track, and performing risk pre-rehearsal in the digital twin; automatically generating a three-level grading prevention and control strategy of prompting, intervention and termination according to the pre-rehearsal result and executing the three-level grading prevention and control strategy, and feeding back the execution result to optimize the model. The application realizes early identification and dynamic closed-loop prevention and control of thermal state operation risks, can advance risk identification by 15-25 minutes, has an identification accuracy rate of high-risk operations of 94.7%, and effectively reduces the accident rate by 73%.

The utility model discloses a fire vehicle -mounted electric rubber dinghy platform relates to fire equipment field, including bottom plate, electric capstan and manual capstan, and the bottom plate top one side is hinged with the storage platform through the rotating shaft, and the bottom plate, electric capstan and manual capstan are all installed at the top of the external fire engine, and the bottom plate includes bottom plate main part, and one side fixed connection of bottom plate main part has hydraulic rod, and hydraulic rod is equipped with two groups and is fixed at one side of bottom plate main part, and electric capstan includes capstan main part, and this platform can utilize the bundle rope and fix electric rubber dinghy on the storage platform surface, when using, can manually rotate and lift the storage platform, utilizes electric capstan to spread the storage platform, and the unfolded storage platform is contacted with the ground, and the fireman is convenient to take down electric rubber dinghy and uses, and the whole operation process is fast and efficient, can all -round improve the efficiency, safety and adaptability of water area rescue action, better guards the life and property safety of the people.

The utility model discloses a kind of operation systems for steel metallurgical industry mixing iron furnace area, comprising: a high corridor;A sampling platform is obtained by being outwardly extended and being arranged from high corridor, and is located the top of track;A lifting baffle, it is located at the front end of tank car direction of one side edge of sampling platform and is set;A sampling groove, it is strip long groove on sampling platform along the extension direction of track, the edge of sampling groove is provided with scale and track along its extension direction;A slider, it is the block structure with through hole in center, it is arranged across sampling groove, for sliding in two tracks correspondingly;Lifting baffle is used to give the guidance of tank car parking position for lowering;Slider is used to move to the best area of sampling according to scale;Sampling rod, vertically insert into the ladle of tank car through the center through hole of slider to sample down.It solves the problem of poor safety of existing mixing iron furnace area work, inconvenient sampling.

The invention relates to the technical field of road tunnel construction traffic control, and provides an intelligent control method of a tunnel intelligent traffic dispersion system in order to solve the problems of low traffic efficiency, large potential safety hazard, incomplete information coverage and the like of an existing inclined shaft and main tunnel intersection. Meanwhile, the driving direction of the vehicle is judged through a direction recognizer; based on the vehicle position and the driving direction, the number of vehicles waiting in line and the vehicle arrival rate are obtained through statistics, calculation is carried out according to an intelligent scheduling algorithm, and the optimal green light prolonging time is obtained; and controlling a traffic light group in the tunnel intelligent traffic dispersion system according to the optimal green light prolonging time, adjusting traffic light timing schemes in the main tunnel direction and the inclined shaft direction, and performing multi-modal information release based on the traffic light timing schemes. According to the invention, the dynamic optimization scheduling of the traffic flow of the tunnel intersection is realized, a non-blind area safety early warning system is constructed, and the traffic efficiency and safety level of the tunnel intersection are remarkably improved.

This utility model discloses an auxiliary unloading mechanism for refrigerated truck compartments, comprising an auxiliary support frame and a multi-functional structure. The bottom of the auxiliary support frame is for contacting the ground, and a transverse transport groove is formed inside the auxiliary support frame. Two insertion slots are formed within the transport groove. The multi-functional structure includes a connecting support frame rotatably connected within the rotating groove. The connecting support frame is made of magnetic material, and a pull plate is connected to the top of the connecting support frame. This utility model, by setting a rotatable connecting support frame and a pull plate and insertion plate that can be magnetically attached to the auxiliary support frame, allows for several advantages. When the multi-functional structure is as shown in Figure 4, workers can pull the pull plate to move the auxiliary support frame, reducing the difficulty of moving it. Furthermore, when the multi-functional structure is as shown in Figure 1, the pull plate can be magnetically attached to the bottom of the refrigerated truck compartment and simultaneously to the insertion slots, increasing the stability of the auxiliary support frame during use.

The utility model discloses a fire-resistant early warning cable, and aims to solve the defect that the existing cable lacks early warning. The cable comprises three cable cores, an early warning optical fiber and a functional layer wrapped outside the cable cores, the three cable cores are attached pairwise, the three cable cores are clamped to form a central space, the early warning optical fiber is arranged in the central space and attached to each cable core, the functional layer comprises a fireproof layer, a fireproof oxygen barrier layer, an oxygen barrier layer, an armor layer and an outer sheath, and the outer sheath is arranged in the fireproof layer. Glass fiber wrapping layers are arranged between the adjacent functional layers and on the inner side of the fireproof layer. According to the cable, hidden dangers of the cable can be found in time through the built-in optical fiber, and the cable has reliable fireproof performance, so that the hidden dangers on the cable can be detected in time, power supply can be maintained in a fire disaster, and in addition, a failure area of the cable can be determined through the built-in optical fiber in a post-accident stage to help to restore the fire behavior.

The application discloses a micro-meteorological perception and multi-agent collaborative decision-making method and system for low-altitude scenes, and belongs to the technical field of low-altitude emergency command and unmanned aerial vehicle cluster scheduling. The system comprises a perception layer, a decision-making layer and an execution layer. The perception layer generates a micro-scale three-dimensional wind field through cascading downscaling, and constructs a voxelized risk cost field based on the wind resistance of unmanned aerial vehicles. The decision-making layer adopts a heterogeneous multi-agent collaborative decision-making engine, realizes the binding of a large language model and a domain calculation model through function interface reasoning double channels, combines a four-stage specialized workflow arrangement, and introduces an unoverlappable meteorological veto mechanism. The execution layer generates simulation verification files and supports dynamic strategy correction. The application solves the problems of insufficient micro-scale meteorological perception accuracy of existing systems, lack of meteorological hard constraints in multi-agent collaboration, and low flight safety resilience, and can be widely applied to low-altitude emergency scenes such as medical material delivery and disaster rescue.

This invention relates to the field of expense reimbursement management technology, and in particular to a centralized management system and method for expense reimbursement documents based on financial sharing. The management system includes a financial sharing module, an interaction management module, and an expense reimbursement document interaction module. The financial sharing module pushes expense reimbursement document data to the interaction management module in real time. The interaction management module controls and monitors the entire interaction process of expense reimbursement documents. The expense reimbursement document interaction module implements the entire interaction process of expense reimbursement documents. A first machine learning model is established in the financial sharing module as its generator network; a second machine learning model is established in the interaction management module as its generator network; a discriminant network for the interaction management module is established in the financial sharing module; and a discriminant network for the financial sharing module is established in the interaction management module. This management system and method effectively solve the problems of risk and time-consuming / labor-intensive processes in expense reimbursement document interaction.

The invention relates to a special operation whole process dynamic risk grading early warning method, system and device, and the method comprises the steps: dividing the whole process of a single special operation into a plurality of continuous operation stages, and recognizing the operation stage of a current operation task; for a current operation task, acquiring and quantifying multi-dimensional risk indexes in real time to form a multi-dimensional risk index value set; according to the operation stage of the current operation task, calling a corresponding weight set from a preset weight configuration library to carry out dynamic risk index calculation so as to obtain a dynamic risk index; and performing graded early warning and strategy matching on the current operation task according to the dynamic risk index. According to the method, a'operation life cycle 'is taken as a time sequence main axis, a dynamic risk index is output through stage adaptive weighting and fusion calculation, and risk management and control of a hierarchical intervention strategy are triggered according to the dynamic risk index, so that risk management is fundamentally converted from static state and single state to dynamic state and comprehensive state, and stage accurate early warning is realized.

The utility model provides a kind of for sintering ring cooling machine discharge port anti -blocking device, belong to sintering ring cooling machine equipment technical field, including controller module, cable, material level meter, alarm, display and discharging timer;The radar material level meter is installed just above the material belt of ring cooling machine, the signal data measured by the material level meter is transmitted to the controller module by the cable, is transmitted to the display by the controller module internal program operation and is shown, if the radar material level meter does not detect the sintered ore material peak value in the time set by the discharging timer, output alarm to the alarm.The utility model is for the special area of ring cooling machine discharge port, when it is impossible to use separate material level meter equipment to measure, prevent the occurrence of ring cooling discharge port blocking accident, improve equipment operation rate, when accident occurs, early prediction is carried out, reduce accident rate and reduce accident handling time, improve sintered ore production has significance.

The utility model provides a floating type wind power platform anchor chain clamping and stabilizing structure and a detection robot. The floating type wind power platform anchor chain clamping and stabilizing structure comprises a clamping and stabilizing device, a visual detection system, a buoyancy adjusting system, a hoisting hook, a control and operation system, a driving wheel and an external frame. The clamping stabilizing device, the buoyancy adjusting system, the hoisting hook, the control operation system and the driving wheel are all installed on the outer frame. The driving system is connected with a sliding block in the clamping and stabilizing device through a driving wheel, and it is ensured that the robot can stably move along the anchor chain. The control operation system is located in the control cabin and connected with the outer frame so as to achieve accurate control over the whole robot. The outer frame is not only used for fixing the robot to the anchor chain, but also optimizes the layout of all the components, so that the overall structure of the robot is compact and efficient, and the stability and reliability of the robot during task execution in a complex marine environment are guaranteed.

The application relates to an offline time detection method, system and medium based on vehicle expected speed, which comprises the following steps: U1. A vehicle travels on a road, real-time acquisition of driving acceleration of the vehicle and heading angle data information of the vehicle based on a vehicle-mounted IMU, and real-time acquisition of position data information of the vehicle based on a vehicle-mounted GPS; U2. Based on the position data information of the vehicle, the driving acceleration of the vehicle and the heading angle data information of the vehicle, a multivariate vehicle expected speed algorithm is used to calculate the expected value of the vehicle speed at different times and positions, so that the expected speed data information of the vehicle at different times and positions is obtained. The application can accurately detect the offline time of the vehicle, and the detection process is suitable for various and complex environments, has a wide application range, and is beneficial to popularization and use.

The utility model relates to the technical field of coal mining discloses a mine gangue pretreatment device with sliding crushing function, including support, set up on the multiaxis mobile structure of support and with the crushing head of multiaxis mobile structure connection, multiaxis mobile structure includes at least the telescopic oil cylinder of horizontal setting on the support, the utility model discloses through setting up the multiaxis mobile structure on the support to control the crushing head, has increased the crushing range, has solved the problem of poor passability of larger coal gangue, personnel waste.

The application discloses a sheep shed road surface recognition method and device for a disinfection robot and a storage medium, and comprises the following steps: generating a binary image by segmenting a sheep shed road image by using a trained recognition model, the binary image being used for visual navigation of a sheep shed disinfection robot; the training steps of the recognition model are as follows: collecting data of a sheep shed internal road image, and performing data enhancement on an original data set; marking and dividing the enhanced image, inputting the processed image into a network model set in advance to train a sheep shed road surface segmentation model; after the training is completed, inputting a test set image to obtain the regression probability of each pixel, and obtaining a binary image by performing binary processing on the prediction result. The application improves the Initial block module, adds SENet, and establishes the mutual dependence relationship between channels in the early stage of the network. Part of the convolution is replaced by a cross attention module, so that the calculation cost is reduced and the performance of network feature extraction is improved.

The invention discloses a tunnel entrance and exit visual buffering illumination system based on light perception, which comprises light-emitting panel groups which are respectively arranged on the inner walls of two ports of a tunnel and comprise light-emitting panels which are laid on the inner walls of the ports in a connected manner; the external photosensitive modules are respectively arranged outside the two ports and are used for collecting brightness outside the tunnel; the internal photosensitive module is installed in the middle section of the tunnel and used for collecting illumination intensity in the tunnel. The vehicle speed measurement modules are installed at the two ports respectively and used for obtaining the vehicle speed. An algorithm module is arranged in the control unit and is used for calculating a target brightness value of each light-emitting panel in the light-emitting panel group according to data acquired by the vehicle speed measurement module, the external light sensing module and the internal light sensing module and adjusting the brightness of the light-emitting panels to form gradient light; and the photovoltaic module supplies power to the light-emitting panel group. The brightness gradient buffer zone is constructed at the entrance and exit of the tunnel, so that eyes of a driver can smoothly adapt to illumination changes when the driver enters and exits the tunnel.

The invention discloses a solar intelligent demisting, deicing and warning all-in-one machine for a road surface. The all-in-one machine comprises a solar power supply and energy storage module; a multi-sensor fusion detection module (temperature and humidity, visibility, road surface temperature and icing); a PTC hot air demisting and ice melting execution module; an automatic warning yellow light module; a 4G / 5G remote data and video return module; the equipment collects environmental parameters in real time, when fog or road icing is judged, hot air and a warning lamp are automatically turned on, data and pictures are uploaded to a control center at the same time, and full-automatic, unattended and large-range networking road safety guarantee is achieved.

The utility model discloses a telescopic protective device of a reversed loader, which belongs to the technical field of safety protection of reversed loaders, and comprises an outer side plate, a left baffle component is fixedly connected to the side surface of the outer side plate and comprises a left telescopic oil cylinder, one end of the left telescopic oil cylinder is fixedly connected with a second left pin shaft, and the other end of the left telescopic oil cylinder is fixedly connected with a second right pin shaft. The side face of the second left pin shaft is rotationally connected with a second left lug plate, the side face of the second left lug plate is fixedly connected with a left extending baffle, and the side face of the left extending baffle is fixedly connected with a left protection plate. A left baffle assembly and a right baffle assembly are fixedly connected to the side face of an outer side plate, a left telescopic oil cylinder and a right telescopic oil cylinder stretch out and draw back, a left protection plate and a right protection plate can be driven to move correspondingly, it is ensured that a dynamic closed space is formed, the accident rate of a dangerous area is reduced, and coal mine safety production is facilitated; and the device can be conveniently fixed at a use place through the connecting holes, and the formed connecting holes are convenient for hoisting.