Method and device for verifying thermal decomposition mechanism of stranded carbon fiber composite core conductor

Abstract

The present application provides a method and apparatus for verifying the thermal decomposition mechanism of a stranded carbon fiber composite core conductor, comprising: performing a thermogravimetric test and analysis on the stranded carbon fiber composite core conductor to be evaluated to obtain thermogravimetric data and a thermal decomposition rate curve; obtaining a reaction mechanism model based on the thermogravimetric data; obtaining a first fitting straight line based on the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor based on the first fitting straight line; obtaining a second fitting straight line based on the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor based on the second fitting straight line; comparing the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, respectively, and verifying the correctness of the reaction mechanism model based on the comparison results. The above method can verify the correctness of the thermal decomposition reaction mechanism model.

Description

Technical Field

[0001] The present invention relates to the field of material analysis, and in particular to a method and device for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor. Background Art

[0002] The stranded carbon fiber composite core conductor is a new type of energy-saving and capacity-enhancing conductor. It features an outer layer of aluminum wire and an inner strand of a multi-strand carbon fiber composite core. Compared to traditional steel-core aluminum stranded wire, this conductor offers advantages such as light weight, high strength, high temperature and corrosion resistance, low line loss, minimal sag, and low cost. It has great potential for application in the retrofitting of legacy lines and in new energy transmission lines.

[0003] The interior of the twisted carbon fiber composite core conductor is mainly made of carbon fiber tow and high-temperature resistant epoxy resin. It is a polymer material. Compared with steel core metal material conductors, it is prone to material aging and limited service life. Carbon fiber composite core conductors are used as overhead transmission lines. During use, they generate high temperature heat through large currents, and polymers are prone to thermal decomposition. When the material thermally decomposes to a certain extent, its performance will degrade to a level that it cannot be used. The service life of a polymer is related to the reaction mechanism model of its material, and the reaction mechanism model of the material represents the thermal decomposition mechanism of the material. However, most of the existing technologies deduce the reaction mechanism model of the material for polymers based on thermal gravimetric testing and thermal decomposition kinetics, but do not provide a method to determine whether the reaction mechanism function is correct. Summary of the Invention

[0004] Based on this, the present invention provides a method and device for verifying the thermal decomposition mechanism of a twisted carbon fiber composite material core conductor, which verifies the correctness of the reaction mechanism model of the twisted carbon fiber composite material core conductor used for overhead transmission lines.

[0005] In a first aspect, the present invention provides a method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor, comprising:

[0006] Performing a thermogravimetric test on the stranded carbon fiber composite material core conductor to be evaluated to obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor;

[0007] Obtaining a reaction mechanism model of the stranded carbon fiber composite material core conductor according to the thermogravimetric data;

[0008] Obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line;

[0009] Obtaining a second fitting straight line according to the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor according to the second fitting straight line;

[0010] The first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor are compared respectively, and the correctness of the reaction mechanism model is verified according to the comparison results.

[0011] Furthermore, obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line, comprises:

[0012] According to the thermal decomposition rate curves at different heating rates, the first fitting straight line was obtained by the Kissinger method;

[0013] A first activation energy is obtained from the slope of the first fitting straight line, and a first pre-exponential factor is obtained from the intercept of the first fitting straight line.

[0014] Furthermore, obtaining a second fitting straight line according to the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor according to the second fitting straight line, includes:

[0015] Obtaining thermogravimetric data at a set heating rate, combining the reaction mechanism model, and processing the data using the Coast-Redfern method to obtain a second fitting line;

[0016] The second activation energy is obtained from the slope of the second fitting straight line, and the second pre-exponential factor is obtained from the intercept of the second fitting straight line.

[0017] In a second aspect, the present invention provides a device for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor, comprising:

[0018] A material testing module is used to perform a thermogravimetric test and analysis on the stranded carbon fiber composite material core conductor to be evaluated, and obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor;

[0019] A model building module, used to obtain a reaction mechanism model of the stranded carbon fiber composite material core conductor based on the thermogravimetric data;

[0020] a first parameter acquisition module, configured to obtain a first fitting straight line according to the thermal decomposition rate curve, and obtain a first activation energy and a first pre-exponential factor according to the first fitting straight line;

[0021] A second parameter acquisition module is used to obtain a second fitting straight line according to the reaction mechanism model, and obtain a second activation energy and a second pre-exponential factor according to the second fitting straight line;

[0022] The model verification module is used to compare the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, and verify the correctness of the reaction mechanism model according to the comparison results.

[0023] The beneficial effect of adopting the above technical solution is: the specific parameters of the first fitting straight line obtained by the thermal decomposition rate curve are compared with the specific parameters of the second fitting straight line obtained by the reaction mechanism model to determine whether the reaction mechanism model of the material is correct, and the thermal decomposition mechanism of the stranded carbon fiber composite core conductor can be more accurately determined based on the reaction mechanism model. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0025] Figure 1 This is a schematic diagram of a method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor in one embodiment of the present application;

[0026] Figure 2 This is the thermal weight loss data of the stranded carbon fiber composite material core conductor in one embodiment of the present application;

[0027] Figure 3 This is a thermal decomposition rate curve of a stranded carbon fiber composite material core conductor in one embodiment of the present application;

[0028] Figure 4 This is a schematic diagram of a first fitting straight line in one embodiment of the present application;

[0029] Figure 5 This is a schematic diagram of a second fitting straight line in one embodiment of the present application;

[0030] Figure 6 Schematic diagram of a device for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor in one embodiment of the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In order to explain the present invention in more detail, the following is a specific description of the method and device for verifying the thermal decomposition mechanism of the twisted carbon fiber composite core conductor provided by the present invention in combination with the drawings.

[0032] Stranded carbon fiber composite conductors are primarily composed of carbon fiber tows and cured with a high-temperature resistant epoxy resin. When used as overhead transmission lines, carbon fiber composite conductors carry high currents, generating high temperatures and susceptible to thermal decomposition of the polymer. Once the thermal decomposition reaches a certain level, its performance degrades to the point where it is unusable. The service life of a polymer is related to its reaction mechanism model, which represents the thermal decomposition mechanism of the material.

[0033] The present application provides an application scenario for a method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite core conductor. This application scenario includes a terminal device provided in the embodiment, including but not limited to a smartphone and a computer device, wherein the computer device can be at least one of a desktop computer, portable computer, laptop computer, mainframe computer, tablet computer, and the like. A user operates the terminal device to verify the correctness of the reaction mechanism model of the carbon fiber composite core conductor. For detailed procedures, please refer to the embodiment of the method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite core conductor.

[0034] Based on this, the embodiment of the present invention provides a method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor. The method is described by taking the application of the method to a terminal device as an example. Figure 1 Schematic diagram of the method for verifying the thermal decomposition mechanism of stranded carbon fiber composite core wires.

[0035] Step S101: performing a thermogravimetric test and analysis on the stranded carbon fiber composite material core conductor to be evaluated to obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor.

[0036] Specifically, step S101 includes the following steps:

[0037] S201: filing the organic fiber filaments wrapped around the surface of the stranded carbon fiber composite material core conductor to be evaluated, and wiping the surface with alcohol.

[0038] Step S202: Grinding the treated stranded carbon fiber composite material core wire to obtain test powder.

[0039] Step S203: After the test powder is dried in a constant temperature drying oven at a set temperature and a set flow rate, the dried test powder is placed in an environment with different heating rates for testing to obtain thermal weight loss data and thermal decomposition rate curves of the stranded carbon fiber composite core conductor at different heating rates.

[0040] The set temperature of the constant temperature drying oven can be 40° C., and the set flow rate of the nitrogen atmosphere can be 100 mL / min.

[0041] The dried test powder is placed in an environment with different heating rates for testing, specifically:

[0042] 5-10 mg of dried test powder were taken and tested at heating rates of 5K / min, 10K / min, 20K / min and 25K / min, respectively. The mass data of the test powder were recorded in the temperature range from room temperature to 900°C.

[0043] Step S102: obtaining a reaction mechanism model of the stranded carbon fiber composite material core conductor according to the thermogravimetric data.

[0044] Specifically, the specific expression of the reaction mechanism model of the stranded carbon fiber composite core conductor is:

[0045]

[0046]

[0047] Among them, G(α) is the reaction mechanism model, α is the reaction conversion rate, which is the ratio of the decomposed mass of the test powder to the total weight loss mass during the thermal decomposition process, m i is the initial mass of the test powder, m is the actual mass of the test powder at a certain moment or temperature during the thermal decomposition process, and m f is the final mass of the test powder after thermal decomposition, and n is the index to be solved, which can be obtained from the thermal gravimetric data of the stranded carbon fiber composite core at different heating rates.

[0048] Step S103: obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line.

[0049] Specifically, step S103 includes the following steps:

[0050] Step S301: obtaining a first fitting straight line by the Kissinger method according to the thermal decomposition rate curves at different heating rates.

[0051] Step S302: obtaining a first activation energy from the slope of the first fitting straight line, and obtaining a first pre-exponential factor from the intercept of the first fitting straight line.

[0052] The specific expression of the above step S103 is:

[0053]

[0054] Where β is the heating rate, T piis the temperature corresponding to the peak value of the thermal decomposition rate curve, A1 is the first pre-exponential factor, E1 is the first activation energy, and R is the thermodynamic constant, R = 8.314 J / (mol·K).

[0055] Step S104: obtaining a second fitting straight line according to the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor according to the second fitting straight line.

[0056] Specifically, step S104 includes the following steps:

[0057] Step S401: obtaining thermogravimetric data of a set heating rate, combining the data with the reaction mechanism model, and processing the data using the Coast-Redfern method to obtain a second fitting line.

[0058] in, and The linear relationship is satisfied, and the reaction mechanism model can obtain a second fitting straight line from the thermogravimetric data at a set heating rate.

[0059] Step S402: obtaining a second activation energy from the slope of the second fitting straight line, and obtaining a second pre-exponential factor from the intercept of the second fitting straight line.

[0060] The specific expression of the above step S104 is:

[0061]

[0062] Where G(α) is the reaction mechanism model, T is the thermodynamic temperature, A2 is the second pre-exponential factor, E2 is the second activation energy, β is the heating rate, and R is the thermodynamic constant, R = 8.314 J / (mol·K).

[0063] Step S105: respectively comparing the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, and verifying the correctness of the reaction mechanism model based on the comparison results.

[0064] Specifically, if the comparison results of the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor meet the following requirements, then the reaction mechanism model is correct;

[0065] The specific expression of the requirement is:

[0066] |E1-E2| / E1≤0.1,

[0067] |lgA1-lgA2| / lgA1≤0.1,

[0068] Wherein, E1 is the first activation energy, E2 is the second activation energy, A1 is the first pre-exponential factor, and A2 is the second pre-exponential factor.

[0069] In order to explain the thermal decomposition mechanism verification method of the stranded carbon fiber composite core conductor in more detail, Figure 2-5 , giving specific examples to illustrate.

[0070] Step S501: Perform a thermogravimetric test on the stranded carbon fiber composite core conductor to be evaluated, and obtain thermogravimetric data and thermal decomposition rate curves of the stranded carbon fiber composite core conductor under heating rate environments of 5K / min, 10K / min, 20K / min and 25K / min. The thermogravimetric data can be found in the attached Figure 2 The thermal decomposition rate curve can be found in the attached Figure 3 .

[0071] Step S502: Obtain a reaction mechanism model of the stranded carbon fiber composite material core conductor based on the thermogravimetric data of step S501. The specific expression is:

[0072]

[0073] Step S503: According to the attached Figure 3 The first fitting straight line is obtained from the temperature data corresponding to the peak value in the thermal decomposition rate curve. The first fitting straight line can be found in the attached Figure 4 The first activation energy E1 = 166.79 kJ / mol is obtained from the slope of the first fitting line, and the first pre-exponential factor A1 = 1.549 × 10 13 s -1 .

[0074] Step S504: Select the thermogravimetric data with a heating rate of 10°C / min, and fit it with the reaction mechanism model of step S502 to obtain a second fitting straight line. The second fitting straight line can be found in the attached figure. Figure 5 The second activation energy E2 = 160.35 kJ / mol is obtained from the slope of the second fitting line, and the second pre-exponential factor A2 = 2.14 × 10 12 s -1 .

[0075] Step S505: Compare the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor respectively, specifically:

[0076]

[0077]

[0078] According to the above comparison results, it can be determined that the reaction mechanism model obtained in step S502 is correct.

[0079] It should be understood that although the Figure 1The steps in the flowchart are shown in the order indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Figure 1 At least part of the steps may include multiple sub-steps or sub-stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0080] The embodiment disclosed in the above invention describes in detail the method for verifying the thermal decomposition mechanism of the stranded carbon fiber composite material core conductor. The method disclosed in the present invention can be implemented using various types of equipment. Therefore, the present invention also discloses a device for verifying the thermal decomposition mechanism of the stranded carbon fiber composite material core conductor corresponding to the above method. Figure 6 , specific embodiments are given below to explain in detail.

[0081] The material testing module 601 is used to perform a thermogravimetric test and analysis on the stranded carbon fiber composite material core conductor to be evaluated, and obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor.

[0082] The model building module 602 is used to obtain a reaction mechanism model of the stranded carbon fiber composite material core conductor according to the thermogravimetric data.

[0083] The first parameter acquisition module 603 is configured to obtain a first fitting straight line according to the thermal decomposition rate curve, and obtain a first activation energy and a first pre-exponential factor according to the first fitting straight line.

[0084] The second parameter acquisition module 604 is configured to obtain a second fitting straight line according to the reaction mechanism model, and obtain a second activation energy and a second pre-exponential factor according to the second fitting straight line.

[0085] The model verification module 605 is used to compare the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, and verify the correctness of the reaction mechanism model according to the comparison results.

[0086] The model verification module 605 includes:

[0087] If the comparison results of the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor meet the following requirements, then the reaction mechanism model is correct;

[0088] The specific expression of the requirement is:

[0089] |E1-E2| / E1≤0.1,

[0090] |lgA1-lgA2| / lgA1≤0.1,

[0091] Wherein, E1 is the first activation energy, E2 is the second activation energy, A1 is the first pre-exponential factor, and A2 is the second pre-exponential factor.

[0092] Regarding the device for verifying the thermal decomposition mechanism of a stranded carbon fiber composite core conductor, all of the above-mentioned methods can be referred to in detail, and will not be further described here. Each module in the above-mentioned device can be implemented in whole or in part through software, hardware, or a combination thereof. Each of the above-mentioned modules can be embedded in or independent of the processor of the terminal device in the form of hardware, or can be stored in the memory of the terminal device in the form of software, so that the processor can call and execute the corresponding operations of each of the above modules.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor, characterized in that: include: Performing a thermogravimetric test on the stranded carbon fiber composite material core conductor to be evaluated to obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor; Obtaining a reaction mechanism model of the stranded carbon fiber composite material core conductor according to the thermogravimetric data; Obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line; Obtaining a second fitting straight line according to the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor according to the second fitting straight line; Comparing the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, respectively, and verifying the correctness of the reaction mechanism model according to the comparison results; Obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line, comprises: According to the thermal decomposition rate curves at different heating rates, the first fitting straight line was obtained by the Kissinger method; Obtaining a first activation energy from the slope of the first fitting straight line, and obtaining a first pre-exponential factor from the intercept of the first fitting straight line; The first fitting straight line is obtained according to the thermal decomposition rate curve, and the first activation energy and the first pre-exponential factor are obtained according to the first fitting straight line. The specific expressions are: , in, is the heating rate, is the temperature corresponding to the peak value of the thermal decomposition rate curve, is the first pre-exponential factor, is the first activation energy, is the thermodynamic constant, ; The comparing the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, respectively, and verifying the correctness of the reaction mechanism model according to the comparison results, includes: If the comparison results of the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor meet the following requirements, then the reaction mechanism model is correct; The specific expression of the requirement is: , , in, is the first activation energy, is the second activation energy, is the first pre-exponential factor, is the second pre-exponential factor.

2. The method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor according to claim 1, wherein: The thermal gravimetric test analysis of the stranded carbon fiber composite material core conductor to be evaluated is performed to obtain thermal gravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor, including: filing the organic fiber filaments wrapped around the surface of the stranded carbon fiber composite material core conductor to be evaluated, and wiping the surface with alcohol; Grinding the treated stranded carbon fiber composite core wire to obtain a test powder; The test powder is placed in a constant temperature drying oven at a set temperature and a set flow rate for drying, and then the dried test powder is placed in an environment with different heating rates for testing to obtain the thermal weight loss data and thermal decomposition rate curves of the stranded carbon fiber composite core conductor at different heating rates.

3. The method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor according to claim 2, wherein: The specific expression of the reaction mechanism model is: , , in, is the reaction mechanism model, is the reaction conversion rate, which is the ratio of the decomposed mass of the test powder to the total weight loss mass during the thermal decomposition process. To test the initial quality of the powder, To test the actual mass of the powder at a certain moment or temperature during the thermal decomposition process, To test the final mass of the powder after thermal decomposition, is the index to be solved.

4. The method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor according to claim 3, wherein: Obtaining a second fitting straight line according to the reaction mechanism model, and obtaining a second activation energy and a second pre-exponential factor according to the second fitting straight line, comprises: Obtaining thermogravimetric data at a set heating rate, combining the reaction mechanism model, and obtaining a second fitting straight line using the Coast-Redfern method; The second activation energy is obtained from the slope of the second fitting straight line, and the second pre-exponential factor is obtained from the intercept of the second fitting straight line.

5. The method for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor according to claim 4, wherein: The second fitting straight line is obtained according to the reaction mechanism model, and the second activation energy and the second pre-exponential factor are obtained according to the second fitting straight line. The specific expressions are: ， in, is the reaction mechanism model, is the thermodynamic temperature, is the second pre-exponential factor, is the second activation energy, is the heating rate, is the thermodynamic constant, .

6. A device for verifying the thermal decomposition mechanism of a stranded carbon fiber composite material core conductor, characterized in that: include: A material testing module is used to perform a thermogravimetric test and analysis on the stranded carbon fiber composite material core conductor to be evaluated, and obtain thermogravimetric data and a thermal decomposition rate curve of the stranded carbon fiber composite material core conductor; A model building module, used to obtain a reaction mechanism model of the stranded carbon fiber composite material core conductor based on the thermogravimetric data; a first parameter acquisition module, configured to obtain a first fitting straight line according to the thermal decomposition rate curve, and obtain a first activation energy and a first pre-exponential factor according to the first fitting straight line; A second parameter acquisition module is used to obtain a second fitting straight line according to the reaction mechanism model, and obtain a second activation energy and a second pre-exponential factor according to the second fitting straight line; A model verification module is used to compare the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, and verify the correctness of the reaction mechanism model according to the comparison results; Obtaining a first fitting straight line according to the thermal decomposition rate curve, and obtaining a first activation energy and a first pre-exponential factor according to the first fitting straight line, comprises: According to the thermal decomposition rate curves at different heating rates, the first fitting straight line was obtained by the Kissinger method; Obtaining a first activation energy from the slope of the first fitting straight line, and obtaining a first pre-exponential factor from the intercept of the first fitting straight line; The first fitting straight line is obtained according to the thermal decomposition rate curve, and the first activation energy and the first pre-exponential factor are obtained according to the first fitting straight line. The specific expressions are: , in, is the heating rate, is the temperature corresponding to the peak value of the thermal decomposition rate curve, is the first pre-exponential factor, is the first activation energy, is the thermodynamic constant, ; The comparing the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor, respectively, and verifying the correctness of the reaction mechanism model according to the comparison results, includes: If the comparison results of the first activation energy and the second activation energy, the first pre-exponential factor and the second pre-exponential factor meet the following requirements, then the reaction mechanism model is correct; The specific expression of the requirement is: , , in, is the first activation energy, is the second activation energy, is the first pre-exponential factor, is the second pre-exponential factor.

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