235 results about "Two temperature" patented technology

The utility model relates to a reaction device capable of quickly heating, cooling and maintaining temperature. According to the reaction device, a three-way valve temperature control device consisting of a set of thermal medium circulator, a set of cold medium circulator, a control unit and two temperature control adjusting motor control three-way valve rotating devices is arranged on the reaction kettle, so that the temperature of the reaction kettle of the reaction device can be increased or decreased within half a minute (even shorter time); the problem that the reaction kettle cannot be rapidly heated and cooled in the reaction process is solved; for heat absorption and heat release experiments, the dynamic balance of the temperature can be maintained by setting a fixed reaction temperature; installation is simple, and operation is convenient; the problem of waste of water resources is solved; the temperature control range is wide, and when a water medium is used, the temperature control range is 1-95 DEG C; when a silicone oil medium is used, the temperature control range is-50 to 250 DEG C; the rotatable distillation head is mounted at the upper part of the reaction kettle and is directly rotated during use, so that the functions of condensation reflux and distillation extraction can be simultaneously realized.

The invention relates to the technical field of refrigerator control, in particular to a double-temperature-zone refrigerator temperature control method and a refrigerator, and the method comprises the steps: obtaining a temperature value and a target temperature value of each temperature control zone, and setting a state vector of each temperature control zone; according to the state vector of each temperature control subarea, determining an initial control strategy of each temperature control subarea according to the air circulation condition in the temperature control subarea; traversing the initial control strategy according to the actual operation time of the initial control strategy, and checking the strategy interaction degree of each temperature control partition; extracting a phase difference condition of each temperature control subarea under the strategy interaction degree, and identifying a control adjustment mode of the current temperature control subarea according to an execution time length value under the phase difference condition; based on the target adjustment temperature of the control adjustment mode, checking the resource matching degree of each temperature control partition, and outputting an adjusted control strategy corresponding to each temperature control partition according to the resource matching degree; efficiency and accuracy of temperature control of the double-temperature-zone refrigerator are achieved.

The present invention relates to a temperature control system (100) for controlling the temperature of workpieces, in particular for heating vehicle bodies, wherein the temperature control system (100) comprises the following: - at least two temperature control modules (104) which are located one behind the other in a direction of travel (102); and - at least one power module (105) for circulating and controlling the temperature of recirculation air, said power module being placed at least in part between the at least two temperature control modules (104), wherein the at least two temperature control modules (104) and the at least one power module (105) form a temperature control chamber (106) through which the workpieces can be conveyed along the direction of travel (102) in order for their temperature to be controlled by recirculation air. The present invention also relates to a corresponding method for controlling the temperature of workpieces, in particular for heating vehicle bodies.

The optical element detection device and the optical element detection method are high in testing efficiency and accuracy, the optical element detection device comprises a measuring assembly and a temperature control assembly, and a containing cavity of the temperature control assembly is used for fixing and containing an optical element to be tested and used for adjusting the temperature in the containing cavity. The measuring assembly is used for detecting deviation of optical parameters of the optical element at different environment temperatures. The temperature control assembly comprises a first temperature adjusting module and a second temperature adjusting module, the first temperature adjusting module adjusts the temperature in the containing cavity in a heat conduction mode, the second temperature adjusting module adjusts the temperature in the containing cavity in a heat convection mode, and the efficiency and accuracy of temperature adjustment in the temperature control assembly are effectively improved through cooperation of the two temperature adjusting modules. Therefore, the testing efficiency of the optical parameters of the optical element at different environment temperatures is improved.

The invention discloses a control method and device of electrical equipment, the electrical equipment and a storage medium. The electrical equipment comprises a shell, a temperature measurement module and a controller. The shell is provided with a first surface and a second surface which deviate from each other. The temperature measurement module is arranged on the first surface and comprises a first temperature measurement unit and a second temperature measurement unit, and the two temperature measurement units define a heat transfer channel. The controller is used for acquiring a first temperature corresponding to the first temperature measuring unit and a second temperature corresponding to the second temperature measuring unit; and when the determined temperature of the heated object is greater than the reference temperature, correcting the temperature measurement model based on the first temperature, the second temperature and the reference temperature. The reference temperature represents the maximum temperature value which can be reached by the electrical equipment in the current working mode. And if the determined temperature of the heated object is greater than the reference temperature, the temperature measurement model has deviation. And the controller corrects the temperature measurement model so as to ensure that the corrected temperature measurement model can accurately determine the temperature of the heated object.

The invention relates to the technical field of intelligent regulation and control, in particular to an intelligent regulation and control method for an active heat storage and release system of a large arched shed framework, and the method comprises the steps: obtaining temperature data of a large arched shed at each sampling moment, and obtaining a temperature data sequence in a historical time period; obtaining an optimized distance measure between every two pieces of temperature data in the temperature data sequence, clustering the temperature data sequence to obtain a preset number of clusters, and determining a heat storage and release state corresponding to each cluster according to a cluster center of each cluster; and real-time temperature data of the large arched shed are obtained, a target heat storage and release state corresponding to the real-time temperature data is determined according to the distance between the real-time temperature data and the cluster center of each cluster, and the large arched shed framework active heat storage and release system is intelligently regulated and controlled according to the target heat storage and release state. The accuracy of heat storage and release state recognition based on the clustering result is improved, and finer and more efficient temperature regulation and control are achieved.

The invention relates to a food maturity detection method and device, a steaming oven and computer equipment, the food maturity detection method and device are applied to the steaming oven comprising a temperature probe, at least two temperature measurement modules are arranged at different positions of the temperature probe, and the food maturity detection method comprises the steps that in the process of heating an inner container of the steaming oven, temperature parameters collected by all the temperature measurement modules are obtained; wherein based on the relative position information of the temperature probe and the food to be measured, the internal temperature and the surface temperature of the food to be measured are respectively calculated through all the temperature measuring modules; and adjusting the working state of the steaming oven according to a preset target temperature and the collected internal temperature and surface temperature until the to-be-detected food is cooked. By adopting the method, the internal maturity and the surface maturity of the food can be considered in the heating process, and the user experience is effectively improved.

The present invention relates to a temperature control system (100) for temperature control of workpieces, in particular for heating vehicle bodies, wherein the temperature control system (100) comprises the following: - at least two temperature control modules (104) arranged one behind the other in a conveying direction (102); and - at least one power module (105) for circulating and tempering recirculated air, which is arranged at least sectionally between the at least two tempering modules (104), wherein the at least two tempering modules (104) and the at least one power module (105) form a tempering chamber (106) through which the workpieces can be conveyed for tempering with recirculated air along the conveying direction (102). Furthermore, the present invention relates to a corresponding method for tempering workpieces, in particular for heating vehicle bodies.

The invention particularly relates to a resistance furnace temperature control method based on IMC-PID feedforward decoupling. The method comprises the steps that temperature curves of a first temperature interval and a second temperature interval which are coupled in a resistance furnace are collected; constructing a mathematical model of the system based on the temperature curve; based on the mathematical model of the system, establishing a feed-forward decoupling compensator by adopting a feed-forward compensation decoupling method; the system is decoupled through a feedforward decoupling compensator, and a decoupled mathematical model is obtained; and an IMC-PID controller is adopted to control the decoupled mathematical model, and independent temperature control over the first temperature interval and the second temperature interval is achieved. The method is simple and easy to implement, and can eliminate the condition of temperature interval coupling under the condition that a mathematical model is not accurate, so that the temperatures of the two temperature intervals are accurately controlled.

The embodiment of the invention belongs to the technical field of household appliances, and provides a refrigerator, a refrigerator door seal cold leakage detection method and a storage medium. The refrigerator comprises a refrigerator body provided with a storage chamber, a door body used for opening or closing the storage chamber, a door sealing strip arranged on the door body, a control assembly arranged in the refrigerator body and multiple sets of temperature sensors arranged in the storage chamber, any set of temperature sensors comprises two temperature sensors, one temperature sensor is close to the door sealing strip, and the other temperature sensor is close to the door sealing strip. And the other temperature sensor is far away from the door gasket. And the control assembly is configured to acquire a plurality of temperature values through the plurality of groups of temperature sensors, determine a temperature difference value corresponding to each group of temperature sensors, and determine whether the door seal leaks cold or not according to the plurality of temperature difference values corresponding to the plurality of groups of temperature sensors. Whether the door seal leaks cold or not can be automatically detected through the multiple sets of temperature sensors, and the influence of cold leakage of the door seal on the refrigerating efficiency of the refrigerator can be reduced.

The invention relates to the field of air-cooled cupboard control, and particularly discloses a control system of a double-temperature air-cooled cupboard, comprising: a refrigeration starting module, which matches fan operation parameters through a difference value between an actually measured temperature of a temperature zone and a set temperature, and adaptively adjusts the fan operation parameters based on a cooling speed; the defrosting trigger module fuses triple parameters of compressor operation duration, evaporator temperature and frosting thickness, and analyzes and evaluates defrosting strength according to dynamic weighted fusion; the defrosting regulation and control module is used for initially setting defrosting parameters according to the defrosting force, estimating the temperature rise amplitude of a refrigeration area and adjusting the defrosting parameters in combination with a machine learning model, and selecting a low-interference time period for defrosting according to the opening frequency of a cabinet door; the defrosting ending module monitors the temperature of the temperature zone and the evaporator in real time, and defrosting is stopped in advance when the threshold value is exceeded. The dynamic balance problem of a single-system double-temperature area during synchronization of refrigeration and freezing defrosting is solved, accurate temperature control is achieved, energy consumption is reduced, and operation is simplified.

The invention relates to a steam sterilization method and system for a reusable medical instrument. The method comprises the following steps: collecting at least two temperature values of a sterilization chamber of sterilization equipment and at least two pressure values of steam pressure of the sterilization chamber; calculating the at least two temperature values and the at least two pressure values based on a preset risk prediction model, and determining a temperature uniformity safety margin and a temperature fluctuation margin; and determining an alarm threshold value based on a temperature uniformity reference threshold value of a temperature uniformity safety margin and / or a sterilization temperature fluctuation threshold value of a temperature fluctuation margin, the alarm threshold value being close to the temperature uniformity reference threshold value or the sterilization temperature fluctuation threshold value, so that the sterilization equipment is debugged before a fault occurs. According to the invention, maintenance personnel can be timely notified to carry out debugging before the sterilization equipment has a real fault, the influence of temperature on hardware equipment of the sterilization equipment is reduced, the service life is prolonged, and the stability of the sterilization effect can be timely maintained through debugging.

The present invention relates to a temperature control system (100) for controlling the temperature of workpieces, in particular for heating vehicle bodies, wherein the temperature control system (100) comprises the following: - at least two temperature control modules (104) which are located one behind the other in a direction of travel (102); and - at least one power module (105) for circulating and controlling the temperature of recirculation air, said power module being placed at least in part between the at least two temperature control modules (104), wherein the at least two temperature control modules (104) and the at least one power module (105) form a temperature control chamber (106) through which the workpieces can be conveyed along the direction of travel (102) in order for their temperature to be controlled by recirculation air. The present invention also relates to a corresponding method for controlling the temperature of workpieces, in particular for heating vehicle bodies.

The present application provides a mutual calibration method, system, and electronic device for air conditioning temperature sensors, comprising the following steps: when the current environment meets the calibration start conditions for the temperature sensors, obtaining measurement correction values ​​of at least two temperature sensors at the current temperature point; obtaining the ambient temperature measurement value of the temperature sensor based on the measurement correction value; updating the calibration compensation value of each temperature sensor at the current temperature point based on the ambient temperature measurement value; obtaining the calibration compensation value of each temperature sensor at other temperature points based on the calibration compensation value of the current temperature point; and screening the calibration compensation values ​​of all temperature points to control the temperature measurement error between each temperature sensor. The mutual calibration method, system, and electronic device for air conditioning temperature sensors of the present application reduce the relative error of the temperature measurement values ​​between the temperature sensors by using the corrected measurement temperature values; making the control of the air conditioning multi-split system more precise, the cooling or heating effect better, and achieving better energy-saving effects.

A method for controlling the casting speed of steel casting by a die casting pouring method belongs to the technical field of die casting production technology in the metallurgical industry and is used to reasonably control the casting speed of steel casting by a die casting pouring method. The technical solution is: a temperature measurement blind hole is opened on the lower side of the ingot mold wall, and two temperature measurement points are formed at different depths along the radial direction. The temperature of the ingot mold wall is continuously and accurately detected during the casting process, and the temperature of the molten steel in the mold is calculated with a delay, thereby adjusting the casting speed of the molten steel in the ladle, controlling the temperature of the molten steel in the ingot mold, and finally achieving uniform solidification of the molten steel, avoiding looseness and shrinkage of the ingot. The present invention is the first of its kind in the die casting pouring method for steel casting, and solves the current urgent problems of timely mastering the temperature measurement of the molten steel pouring process in the ingot mold, monitoring the temperature changes during the entire casting period, and realizing automatic control of the size of the ladle steel flow and the casting speed, providing a reliable technical guarantee for the continuous production of high-quality ingots.

The present invention discloses a coupling operation fault detection method applicable to a wind turbine generator set, which belongs to the technical field of fault detection and includes the following steps: S1, using a temperature sensor to collect the temperature value of the bearing on the coupling; S2, calculating the temperature convergence granularity according to the temperature value of the bearing on the coupling, and determining the upper and lower limits of the temperature convergence interval according to the temperature convergence granularity to generate a temperature convergence interval; S3, judging whether the coupling has a fault based on the temperature convergence interval. The present invention analyzes and processes the temperature value changes at all times according to the temperature value collected by the temperature sensor installed on the coupling bearing, obtains the temperature convergence granularity, obtains two temperature difference values ​​according to the temperature convergence granularity, and finally generates a temperature convergence interval; judging whether the bearing of the coupling has a fault through the temperature convergence interval, timely discovering the operation problem of the coupling, and facilitating the maintenance of the wind turbine generator set.

The invention is a method that comprises at least one cooling element (40) by determining at least two temperature threshold values and providing cooling in case the upper temperature threshold is approached or exceeded and enables the grinder (20) to be heated until it reaches the predetermined temperature in case it is below the mentioned lower temperature threshold in order to prevent the grinding performance from being affected due to temperature change in grinders (20) driven by an AC asynchronous engine (10), wherein; it is to ensure that the engine body (15) is heated with the resulting heat energy by applying voltage to the main winding / windings (11) or one of the auxiliary windings (12) that belong only to said engine (10).

The present application relates to power distribution box temperature monitoring technology, disclose a kind of power distribution box wiring terminal temperature rise early warning method and system.The method is respectively collected temperature in terminal contact area and the position along conductor and leave contact area, and from loop current, identify the rising edge and the unloading edge in pairs;Compare the response of two temperature measuring points in the time of rising, the cooling order of unloading, and calculate the temperature difference integral tail difference after unloading.When the first temperature measuring point is prior to the second temperature measuring point warming, the second temperature measuring point is prior to the first temperature measuring point cooling and the temperature difference integral tail difference exceeds the determination value, and repeat when appearing in multiple load change cycles, output early warning.Thereby, the local heating of contact area can be identified when the absolute temperature of terminal has not reached the fixed high temperature limit, while reducing the false alarm caused by slow change of ambient temperature.

The utility model provides a pregnant woman bellyband with massage and hot compress functions, and belongs to the technical field of pregnant woman supplies, the pregnant woman bellyband comprises a connecting strip, a massage and hot compress assembly and an adjusting assembly, the massage and hot compress assembly comprises a connecting band arranged on one side of two first auxiliary strips, one end of the connecting strip is provided with a protective shell, and a heater is arranged in the protective shell; the heating pad has the advantages that a user presets the temperature through the single-chip microcomputer, when the temperature is too high or high, the temperature sensors feed back information to the single-chip microcomputer, the single-chip microcomputer turns on the temperature controller to adjust the temperature of the heater, and the heating pad is arranged on the heating pad. The temperature control device can effectively prevent a user from being scalded due to the fact that the temperature is too high or can not play a role due to the fact that the temperature is too low, and achieves the purpose of temperature control, thereby achieving the purposes of massage hot compress and temperature control.

The utility model provides an experimental box for exploring factors influencing heat absorption and heat dissipation, which belongs to the technical field of teaching tools and comprises a box body, a bulb, a cross graduated scale, a test box, a temperature sensing module and a display module. Operation openings are formed in four side surfaces of the box body; the bulb is arranged at the middle position in the box body; the cross graduated scale is arranged on the inner wall of the box body, and the bulb is located above the center of the cross graduated scale; the number of the test boxes is at least two, and the test boxes are placed on the cross-shaped calibrated scale and face the bulb. The two temperature sensing modules are correspondingly arranged in the test box; the display module is arranged on the box body and connected with the corresponding temperature sensing module, and the display module is used for displaying the sensing temperature value of the temperature sensing module in real time. According to the utility model, the area factor, the angle factor and the color factor can be tested simultaneously or respectively, so that the same set of teaching aid can be used for exploring the factors related to the heat absorption amount of the solar water heater and exploring the experiment of whether a black object can accelerate heat transfer or not.

This invention discloses a method, device, and control terminal for detecting blanket kicking, belonging to the field of sleep monitoring technology. The blanket kicking detection method includes the following steps: Step S10, acquiring the temperature of the target blanket at each target location; Step S20, calculating the difference between the temperature at each target location and the previously acquired temperature at each target location to obtain the corresponding temperature difference value; Step S30, when at least two of the temperature differences at each target location are greater than a first temperature change threshold, or at least one temperature difference is greater than a second temperature change threshold, it is determined that the target blanket has been kicked off, where the second temperature change threshold is greater than the first temperature change threshold. This invention can continuously and effectively monitor whether a child kicks off their blanket.

The invention discloses a temperature monitoring and control method in a large-volume concrete pouring process of a fan foundation, which belongs to the technical field of fan foundation construction and comprises the following steps: S10, arranging temperature measuring points in the foundation: arranging at least two temperature measuring points along the radial direction of the foundation; s20, test element installation: arranging a first test element for monitoring the atmospheric temperature on the outer side of the foundation; correspondingly installing a second test element at each temperature measurement point in the foundation; s30, constructing a temperature change model; and S40, inputting real-time monitoring data of each monitoring point in the pouring process into the temperature change model, wherein the temperature change model gives an implementation regulation and control scheme. According to the method, the temperature change of mass concrete in the pouring process can be monitored in real time, an accurate regulation and control scheme is given, real-time and accurate monitoring and regulation and control can be achieved, and the construction quality requirement of a wind power foundation is met.

The utility model discloses a linear full-length temperature measurement fire detector. The detector comprises a signal processing module, at least two temperature measurement relay units and at least two temperature measurement cables, the temperature measurement cables and the temperature measurement relay units are alternately arranged, and the temperature measurement cables are electrically connected with the adjacent temperature measurement relay units to form a linear structure; the signal processing module is electrically connected to the head end of the linear structure; the temperature measurement cable is used for collecting first temperature data of a corresponding position of the temperature measurement cable and transmitting the first temperature data to the temperature measurement relay unit; the temperature measurement relay unit is used for collecting second temperature data of the corresponding position of the temperature measurement relay unit and transmitting the first temperature data and the second temperature data to the signal processing module; and the signal processing module is used for determining the highest temperature data on the linear structure according to the first temperature data and the second temperature data, and judging whether fire early warning is carried out or not. According to the technical scheme provided by the embodiment of the utility model, long-distance real-time temperature measurement and fire detection alarm functions can be realized.

Heat exchange device (10) for heating or cooling a fluid, in particular a heating device, comprising a cylindrical chamber (12) through which the fluid flows, with several axially arranged, elongated temperature control elements (28) therein, which form exactly a ring (40) around a central axis (42) of the chamber, and with several guide plates (24) which divide the chamber (12) into several superimposed sub-chambers (38), wherein a flow opening (36) is provided on the outer circumference of each guide plate (24), the shape of which corresponds to the cutting of the guide plate (24) at a secant (44) in order to allow the fluid to flow from one sub-chamber (38) into the next, and wherein the flow openings (36) are arranged alternately on one side and the other side, wherein the flow openings (36) are designed and arranged in such a manner as tothat the temperature control elements (28) are not symmetrical with respect to a connecting line (48) of the flow openings (36) of adjacent guide plates (24), wherein the connecting line (48) is perpendicular to the secant (44), runs through the central axis (42) and is considered in a projection onto a cross-section through the chamber (12), so that the fluid in a flow opening (36) neither flows towards a centrally located temperature control element (28) nor flows centrally between two temperature control elements (28).

The invention relates to a method for managing a sun shield (3), the method comprising a first outside temperature sensor (201) and a second outside temperature sensor (202), and a brightness sensor (220), wherein a control device executes, for each of the two temperature sensors (201, 202): a first step (E1) of measuring the temperature (Ta, Tb); a first analysis step (E2) to determine a variation in the temperature over time; the method comprising the steps of: a second step (E3) of measuring the brightness (L); a second analysis step (E4) to determine a correction coefficient; a step (E5) of determining at least one bias on the basis of the temperatures, the variations and the correction coefficient; a step (E6) of determining an ambient temperature on the basis of the outside temperatures and the bias; a step (E7) of controlling the position of the sun shield (3) depending on the ambient temperature.

The utility model provides a duplex combined temperature controller, and relates to the technical field of temperature controllers. The temperature controller comprises a mounting plate and two temperature controller single bodies, the two temperature controller single bodies are connected to the mounting plate, a client, an external power supply and the two temperature controller single bodies are connected in series, each temperature controller single body comprises a disc, and the capacitance disconnection temperatures of the two discs corresponding to the two temperature controller single bodies are different. One temperature controller single body with relatively low capacitor disconnection temperature can form a temperature controller for starting and closing, the other temperature controller single body can form a temperature controller for equipment protection, and when the temperature controller for starting and closing fails, the temperature controller for equipment protection can form final protection for equipment, so that the temperature controller for equipment protection can be effectively protected. The temperature controller is simple in structure and convenient to use, equipment is prevented from being burnt out at high temperature, damage to electronic components is reduced, the two temperature controller single bodies can be fixed at the same time in a limited installation space through the installation plate, and the space utilization rate is increased.

The utility model discloses a refrigerator defrosting heating pipe additionally provided with temperature controllers, which comprises a defrosting pipe and two groups of temperature controllers, and each temperature controller is provided with two leads which are respectively a black silica gel lead and a 125 DEG C temperature resistant electronic lead; extending leading-out rods are arranged at the two ends of the defrosting pipe, the two temperature controllers are connected to the leading-out rods at the two ends of the defrosting pipe in series respectively, black silica gel wires of the two temperature controllers are electrically connected with the leading-out rods respectively, and therefore safety can be improved, maintenance cost can be reduced, efficiency can be improved, the service life of equipment can be prolonged, the defrosting effect can be improved, and the failure rate can be reduced.

A thermostat device can perform temperature compensation using one or two temperature sensors inside a thermostat device housing to determine an ambient temperature outside the thermostat device housing. A processing circuit of the thermostat device can determine a current operating mode of the thermostat device from a plurality of operating modes. The processing circuit can also estimate a current and a voltage of the thermostat device using machine learning based on a temperature difference between the two temperature sensors. The processing circuit can determine the ambient temperature outside the housing of the thermostat device based at least in part on the estimated current and voltage of the thermostat device and the current operating mode of the thermostat device.

Embodiments of the present invention relate to a method and apparatus for monitoring the ambient temperature of a switch device, comprising: obtaining temperature information collected by two temperature sensors mounted on a PCB board of a target switch device; determining whether an optical module is plugged into the target switch device based on the temperature information; determining an ambient temperature determination strategy based on the determination result; and calculating the ambient temperature of the target switch device using the temperature information based on the determination strategy. Thus, by calculating the ambient temperature based on the relationship between the ambient information and the temperature of the PCB board's air inlet and outlet, the ambient temperature can be calculated based on the air inlet and outlet temperatures, enabling ambient temperature monitoring for devices with high power consumption and high-density port layouts.

The invention discloses a monitoring system and method for heat circulation of a welding heat affected zone and a related device, and relates to the technical field of heat circulation monitoring of the welding heat affected zone, the system comprises a welding test plate set, a thermocouple, a compensation wire and a temperature monitoring device, each welding test plate of the welding test plate set at least comprises a temperature measuring hole, the temperature measuring hole at least comprises two temperature measuring points arranged according to a preset distribution rule, each temperature measuring point is connected with a thermocouple, the thermocouples are connected with temperature monitoring equipment through compensation wires, and in the welding process, the thermocouples collect thermal cycle data of the temperature measuring points and send the thermal cycle data to the temperature monitoring equipment. The thermal cycle data is displayed by a temperature display in the device. The temperature measuring points are arranged at the temperature measuring holes of the welding test plate, the thermocouples are connected to the temperature measuring points, the thermal cycle data of the welding heat affected zone are obtained in real time in the welding process, monitoring of the welding heat affected zone is achieved, and therefore the welding quality is ensured, and the hardening problem and the cold crack condition are prevented.