阅读说明：本技术 一种常温固化的中子屏蔽材料及其制备方法 (Normal-temperature cured neutron shielding material and preparation method thereof ) 是由 郭亮亮 刘志远 周如东 张睿 倪维良 朱亚君 于 2021-09-02 设计创作，主要内容包括：本发明属于核辐射屏蔽材料技术领域,具体涉及一种常温固化的中子屏蔽材料及其制备方法。其常温固化的中子屏蔽材料以重量份计包括以下原料：基体40-52重量份,中子吸收剂4-7重量份,催化剂0.5-1.0重量份,还原氧化石墨烯2-4重量份；其中所述基体包括苯基乙烯基硅油30-39重量份,苯基含氢硅油10-13重量份。由于采用苯基乙烯基硅油作为基本树脂,在铂金催化剂的作用下,与苯基含氢硅油在常温下发生硅氢加成反应,即实现了本发明常温条件下的固化,本材料使用的还原氧化石墨烯可使其耐γ射线辐射能力增强。(The invention belongs to the technical field of nuclear radiation shielding materials, and particularly relates to a normal-temperature cured neutron shielding material and a preparation method thereof. The neutron shielding material cured at normal temperature comprises the following raw materials in parts by weight: 40-52 parts of a matrix, 4-7 parts of a neutron absorber, 0.5-1.0 part of a catalyst and 2-4 parts of reduced graphene oxide; wherein the matrix comprises 30-39 parts by weight of phenyl vinyl silicone oil and 10-13 parts by weight of phenyl hydrogen silicone oil. As the phenyl vinyl silicone oil is used as basic resin and is subjected to hydrosilylation reaction with the phenyl hydrogen-containing silicone oil at normal temperature under the action of the platinum catalyst, the curing at normal temperature is realized, and the reduced graphene oxide used by the material can enhance the gamma-ray radiation resistance.)

1. The neutron shielding material cured at normal temperature is characterized by comprising the following raw materials in parts by weight: 40-52 parts of a matrix, 4-7 parts of a neutron absorber, 0.5-1.0 part of a catalyst and 2-4 parts of reduced graphene oxide; wherein the matrix comprises 30-39 parts by weight of phenyl vinyl silicone oil and 10-13 parts by weight of phenyl hydrogen silicone oil.

2. The ambient-temperature-curing neutron shielding material according to claim 1, wherein the phenyl vinyl silicone oil has a molecular structure ofWherein the molecular weight of the phenyl vinyl silicone oil is between 2500-4000; the content of the vinyl is 0.6 to 1.1 percent.

3. The ambient-cured neutron shielding material of claim 1, wherein the neutron absorber comprises one or more of gadolinium oxide, boron carbide, and boron nitride.

4. The ambient-temperature-curing neutron shielding material according to claim 1, wherein the catalyst comprises one or more of three transition metal complex aqueous solutions of Pt, Pd and Rh, and the concentration of the complex aqueous solution is 3000ppm to 7000 ppm.

5. The ambient-temperature-curing neutron shielding material according to claim 1, wherein the raw materials further comprise 4-7 parts by weight of reinforcing fibers, 31-45 parts by weight of flame retardants, and 0.5-1.0 part by weight of anti-settling agents.

6. The ambient-temperature-curing neutron shielding material according to claim 5, wherein the reinforcing fibers comprise one or more of sepiolite fibers, glass fibers, and silicate fibers; the length of the reinforcing fiber is 0.6-2 mm.

7. The ambient-temperature-curing neutron shielding material according to claim 5, wherein the anti-settling agent comprises one or more of hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, Garamite 1958.

8. The ambient-temperature-curing neutron shielding material according to claim 5, wherein the flame retardant comprises one or more of zinc borate, magnesium hydroxide and antimony trioxide.

9. A method for preparing the ambient-temperature-curing neutron shielding material according to any one of claims 1 to 8, comprising the following steps:

step S1, sequentially adding phenyl vinyl silicone oil, a neutron absorber, a reinforcing fiber, a flame retardant, reduced graphene oxide and an anti-settling agent into a vacuumized stirring device, vacuumizing, and stirring to obtain a mixture;

step S2, after pressure is released, adding phenyl hydrogen-containing silicone oil and a catalyst into the mixture prepared in the step S1, vacuumizing, starting stirring;

and step S3, keeping vacuum for a period of time after stopping stirring, taking out after pressure relief, and carrying out standing and curing treatment at normal temperature to obtain the neutron shielding material cured at normal temperature.

10. The production method according to claim 9, wherein in steps S1-S3, the degree of vacuum of the stirring device is < 0.015 MPa.

Technical Field

The invention belongs to the technical field of nuclear radiation shielding materials, and particularly relates to a normal-temperature cured neutron shielding material and a preparation method thereof.

Background

Neutrons are one of the basic particles constituting atomic nuclei, and because they are uncharged, even if the energy is very low, they can also cause nuclear reactions, so that they are widely used in the field of nuclear power generation, and provide a large amount of efficient energy for human production and life. While the use of neutrons is convenient, it also creates many hazards: materials subjected to neutron irradiation in the containment vessel of the nuclear power station for a long time have internal defects and dislocation, so that equipment failure and even nuclear accidents are caused; neutron irradiation also can cause great harm to human bodies, and human cell tissues can be damaged by secondary particles generated by neutron ionization; therefore, during the operation of the nuclear power plant, neutron shielding materials are needed to shield and protect internal areas or facilities of the nuclear power plant.

At present, the neutron shielding materials at home and abroad have more types and different performances, such as: the metal neutron shielding material and the neutron shielding glass have poor flexibility; the shielding material of the protective fiber class has better flexibility but weaker shielding performance; the epoxy resin system neutron shielding material has poor heat resistance; the cement-based neutron shielding material has huge volume and a bloated structure. Meanwhile, due to the limitation of construction technology and use environment, the neutron shielding material is difficult to simultaneously meet the requirements of high temperature resistance and complex shielding and protecting structure. Therefore, there is a need to develop a neutron shielding material applied to the interior of a containment vessel of a nuclear power plant, which has excellent neutron shielding performance and can be cured at normal temperature to meet the performance requirements of cast-in-place construction.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the neutron shielding material cured at normal temperature is provided to solve the problems that the existing material can not be cured at normal temperature and cast in situ.

The technical scheme adopted by the invention for solving the technical problems is as follows: the neutron shielding material cured at normal temperature comprises the following raw materials in parts by weight: 40-52 parts of a matrix, 4-7 parts of a neutron absorber, 0.5-1.0 part of a catalyst and 2-4 parts of reduced graphene oxide; wherein the matrix comprises 30-39 parts by weight of phenyl vinyl silicone oil and 10-13 parts by weight of phenyl hydrogen silicone oil.

Further, the molecular structure of the phenyl vinyl silicone oil isWherein the molecular weight of the phenyl vinyl silicone oil is between 2500-4000; the content of the vinyl is 0.6 to 1.1 percent.

Further, the neutron absorber includes one or more of gadolinium oxide, boron carbide, and boron nitride. Gadolinium oxide is preferably used in the material, the gadolinium oxide is an excellent neutron absorber, the average neutron absorption cross section of gadolinium element is 36300Barn, the gadolinium element is an element with the best known neutron absorption performance in nature, and the prepared material has excellent neutron absorption performance.

Further, the catalyst comprises one or more of three transition metal complex aqueous solutions of Pt, Pd and Rh, and the concentration of the complex aqueous solution is 3000ppm-7000 ppm. As an alternative embodiment of the catalyst, Pt is preferably selected as the catalyst, and the catalytic performance of the catalyst is good.

Furthermore, the raw materials also comprise 4-7 parts by weight of reinforcing fiber, 31-45 parts by weight of flame retardant and 0.5-1.0 part by weight of anti-settling agent.

Further, the reinforcing fiber comprises one or more of sepiolite fiber, glass fiber and silicate fiber, and the length of the reinforcing fiber is 0.6-2 mm. Preferably, the sepiolite can be selected as the reinforcing fiber, the sepiolite has good heat resistance, good ion exchange and catalytic properties, and excellent properties such as corrosion resistance, radiation resistance, insulation and heat insulation, particularly, Si-OH in the structure of the sepiolite can directly react with organic matters to generate organic mineral derivatives, the reinforcing fiber is uniformly distributed in the material, the skeleton supporting effect can be achieved, the defect that the structural strength of the material is low is effectively overcome, and after the reinforcing fiber is added, the bending strength and the tensile strength of the neutron shielding material are obviously improved.

Further, the anti-settling agent comprises one or more of hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, Garamite 1958. Preferably, Garamite1958 from ROCKWOOD, inc, is selected as the anti-settling agent, and Garamite1958 has unique rheological properties that ensure excellent sag resistance and anti-settling properties of the system, whether at high or low viscosity, and requires agitation to disperse after addition to the matrix.

Further, the flame retardant comprises one or more of zinc borate, magnesium hydroxide and antimony trioxide. Preferably, Mg (OH) is selected₂And B₂O₆Zn₃As the composite flame retardant, the two have excellent temperature resistance; mg (OH)₂Heated, dehydrated and decomposed, can effectively inhibit the temperature rise and thermal degradation of the shielding material, has good flame retardant effect, and simultaneously Mg (OH)₂The material contains H elements, and the H elements with low atomic numbers have obvious moderating effect on fast neutrons, thereby being beneficial to improving the moderating performance of the fast neutrons; b is₂O₆Zn₃Under high temperature, forming glass state inorganic coating to block volatile combustible material from escaping and prevent oxidation reaction, and B₂O₆Zn₃B contained in (A) and (B)₁₀The element is a high-efficiency neutron absorber, and is beneficial to improving the neutron absorption performance of the material.

In another aspect, the present invention further provides a method for preparing a normal temperature cured neutron shielding material, which is used for preparing the normal temperature cured neutron shielding material, and includes the following steps: step S1, sequentially adding phenyl vinyl silicone oil, a neutron absorber, a reinforcing fiber, a flame retardant, reduced graphene oxide and an anti-settling agent into a vacuumized stirring device, vacuumizing, and stirring to obtain a mixture; step S2, after the pressure of the equipment is released, adding phenyl hydrogen-containing silicone oil and a catalyst into the mixture prepared in the step S1 according to the weight percentage content, vacuumizing, starting stirring; and step S3, keeping vacuum for a period of time after stopping stirring, taking out after pressure relief, and standing at normal temperature for curing treatment to obtain the neutron shielding material. Wherein in the steps S1-S3, the vacuum degree of the stirring device is less than 0.015 MPa.

The reduced graphene oxide is also used in the material to enhance the radiation resistance of the neutron shielding material cured at normal temperature, and each carbon atom in the reduced graphene oxide is SP²Hybridization is carried out to form a large pi bond, so that the energy generated by absorbing gamma rays can be transferred in molecules, the molecular structure is not destroyed, and the gamma ray radiation resistance of the material is improved.

The invention has the beneficial effects that: according to the normal-temperature cured neutron shielding material, the phenyl vinyl silicone oil is used as the basic resin, and the phenyl vinyl silicone oil and the phenyl hydrogen-containing silicone oil can generate hydrosilylation reaction at normal temperature under the action of the platinum catalyst and vacuum reaction, so that the curing of the normal-temperature cured neutron shielding material at normal temperature is realized, the material can be directly constructed on site, and the construction performance of the material is greatly improved. The reduced graphene oxide used in the material can enhance the gamma-ray radiation resistance, the finished product has good neutron shielding effect and outstanding temperature resistance, the finished product can operate in a high-temperature environment, and the product performance can meet the technical index requirements of a nuclear power station.

Detailed Description

The present invention will now be described in detail to make the objects, technical solutions and advantages of the embodiments of the present invention clearer. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

On the basis of the formula, 5 specific proportions are selected, and the normal-temperature-cured neutron shielding material of the embodiments 1 to 5 is prepared according to the preparation method.

Example 1

(1) Adding 30.0 parts of phenyl vinyl silicone oil, 4.0 parts of neutron absorber gadolinium oxide, 4.0 parts of reinforcing fiber sepiolite fiber, 25.0 parts of flame retardant zinc borate, 20.0 parts of flame retardant magnesium hydroxide, SE 14304.0 parts of reduced oxyalkylene and Garamite19582.0 parts of anti-settling agent into stirring equipment capable of being vacuumized, starting stirring, and stirring for 5-15min at the rotating speed of 600 plus 800 r/min;

(2) vacuumizing and stabilizing the absolute vacuum degree to be less than 0.015MPa, stirring for 30-50min, stopping stirring, and opening an emptying valve to normal pressure;

(3) adding 10.0 parts of phenyl hydrogen-containing silicone oil and 1.0 part of platinum catalyst, vacuumizing to ensure that the absolute vacuum degree is stabilized to be less than 0.015MPa, starting stirring and wall scraping, stirring for 10-20min at the rotation speed of 600 plus 800r/min, and controlling the material temperature to be between 10 and 40 ℃ in the stirring process;

(4) stopping stirring, keeping the absolute vacuum degree, standing for 5-10min, then opening an emptying valve to normal pressure, lifting and stirring, pouring into a mold, and standing for 24h to obtain the normal-temperature cured neutron shielding material of the embodiment 1.

Example 2

(1) Adding 36.0 parts of phenyl vinyl silicone oil, 5.5 parts of neutron absorber gadolinium oxide, 5.6 parts of reinforcing fiber sepiolite fiber, 20.0 parts of flame retardant zinc borate, 16.0 parts of flame retardant magnesium hydroxide, SE 14303.0 parts of reduced oxyalkylene and 81.2 parts of anti-settling agent Garamite19581.2 into stirring equipment capable of being vacuumized, starting stirring, and stirring for 5-15min at the rotating speed of 600-800 r/min;

(2) vacuumizing and stabilizing the absolute vacuum degree to be less than 0.015MPa, stirring for 30-50min, stopping stirring, and opening an emptying valve to normal pressure;

(3) adding 12.0 parts of phenyl hydrogen-containing silicone oil and 0.7 part of platinum catalyst, vacuumizing to ensure that the absolute vacuum degree is stabilized to be less than 0.015MPa, starting stirring and wall scraping, stirring for 10-20min at the rotation speed of 600 plus 800r/min, and controlling the material temperature to be between 10 and 40 ℃ in the stirring process;

(4) stopping stirring, keeping the absolute vacuum degree, standing for 5-10min, then opening an emptying valve to normal pressure, lifting and stirring, pouring into a mold, and standing for 24h to obtain the normal-temperature cured neutron shielding material of the embodiment 2.

Example 3

(1) Adding 39.0 parts of phenyl vinyl silicone oil, 7.0 parts of neutron absorber gadolinium oxide, 7.0 parts of reinforcing fiber sepiolite fiber, 16.0 parts of flame retardant zinc borate, 15.0 parts of flame retardant magnesium hydroxide, SE 14302.0 parts of reduced oxyalkylene and 19580.5 parts of anti-settling agent GaramiteS into stirring equipment capable of being vacuumized in sequence, starting stirring, and stirring for 5-15min at the rotating speed of 600-800 r/min;

(2) vacuumizing and stabilizing the absolute vacuum degree to be less than 0.015MPa, stirring for 30-50min, stopping stirring, and opening an emptying valve to normal pressure;

(3) adding 13.0 parts of phenyl hydrogen-containing silicone oil and 0.5 part of platinum catalyst, vacuumizing to ensure that the absolute vacuum degree is stabilized to be less than 0.015MPa, starting stirring and wall scraping, stirring for 10-20min at the rotation speed of 600 plus 800r/min, and controlling the material temperature to be between 10 and 40 ℃ in the stirring process;

(4) stopping stirring, keeping the absolute vacuum degree, standing for 5-10min, then opening an emptying valve to normal pressure, lifting and stirring, pouring into a mold, and standing for 24h to obtain the normal-temperature cured neutron shielding material of the embodiment 3.

Example 4

(1) Sequentially adding 30.0 parts of phenyl vinyl silicone oil, 4.0 parts of neutron absorber gadolinium oxide, 4.0 parts of reinforcing fiber sepiolite fiber, 16.0 parts of flame retardant zinc borate, 15.0 parts of flame retardant magnesium hydroxide, SE 14302.0 parts of reduced oxyalkylene and 19580.5 parts of anti-settling agent Garamite19580.5 into stirring equipment capable of being vacuumized, starting stirring, and stirring for 5-15min at the rotating speed of 600-800 r/min;

(2) vacuumizing and stabilizing the absolute vacuum degree to be less than 0.015MPa, stirring for 30-50min, stopping stirring, and opening an emptying valve to normal pressure;

(3) adding 10.0 parts of phenyl hydrogen-containing silicone oil and 0.5 part of platinum catalyst, vacuumizing to ensure that the absolute vacuum degree is stabilized to be less than 0.015MPa, starting stirring and wall scraping, stirring for 10-20min at the rotation speed of 600 plus 800r/min, and controlling the material temperature to be between 10 and 40 ℃ in the stirring process;

(4) stopping stirring, keeping the absolute vacuum degree, standing for 5-10min, then opening an emptying valve to normal pressure, lifting and stirring, pouring into a mold, and standing for 24h to obtain the normal-temperature cured neutron shielding material of the embodiment 4.

Example 5

(1) Adding 39.0 parts of phenyl vinyl silicone oil, 7.0 parts of neutron absorber gadolinium oxide, 7.0 parts of reinforcing fiber sepiolite fiber, 25.0 parts of flame retardant zinc borate, 20.0 parts of flame retardant magnesium hydroxide, SE 14304.0 parts of reduced oxyalkylene and 19582.0 parts of anti-settling agent Garamite1950 into stirring equipment capable of being vacuumized, starting stirring, and stirring for 5-15min at the rotating speed of 600-800 r/min;

(2) vacuumizing and stabilizing the absolute vacuum degree to be less than 0.015MPa, stirring for 30-50min, stopping stirring, and opening an emptying valve to normal pressure;

(3) adding 13.0 parts of phenyl hydrogen-containing silicone oil and 1.0 part of platinum catalyst, vacuumizing to ensure that the absolute vacuum degree is stabilized to be less than 0.015MPa, starting stirring and wall scraping, stirring for 10-20min at the rotation speed of 600 plus 800r/min, and controlling the material temperature to be between 10 and 40 ℃ in the stirring process;

(4) stopping stirring, keeping the absolute vacuum degree, standing for 5-10min, then opening an emptying valve to normal pressure, lifting and stirring, pouring into a mold, and standing for 24h to obtain the normal-temperature cured neutron shielding material of the embodiment 5.

The raw materials used for the normal temperature curing neutron shielding materials of the embodiments 1 to 5 are all commercial industrial products except for other descriptions, and can be purchased from commercial channels. The raw materials are derived from the following sources: the phenyl vinyl silicone oil DS12551-2KH is the product brand of MeiWo company of Wuhan family; the phenyl hydrogen-containing silicone oil IOTA232 is a product brand of Anhui Eyota company; the neutron absorber gadolinium oxide is an 800-mesh product produced by ZiboLei nano-material Co.Ltd; the flame retardant zinc borate is a 800-mesh product produced by Lanzhou yellow river zinc magnesium nano material research institute, and the flame retardant magnesium hydroxide is a 400-mesh product produced by Zehui chemical company; reduced oxidized limonene SE1430 is 1250 mesh product produced by Heizhou sixth element material science and technology corporation; the anti-settling agent Garamite1958 is a product brand of ROCKWOOD company, and is aluminum-magnesium modified organic bentonite; the platinum catalyst is 5000ppm product produced by Mei Wao company of Wuhan Ke.

The normal temperature cured neutron shielding material of the present invention is improved in view of the disadvantages of the conventional neutron shielding material, and the present invention is further described below with reference to the normal temperature cured neutron shielding materials prepared in examples 1 to 5, but is not limited thereto. The normal temperature cured neutron shielding materials prepared in examples 1-5 were used as a comparison sample for testing the mechanical, thermal, radiation-resistant and neutron shielding properties of the normal temperature cured neutron shielding material of the present invention, and the test results are shown in table 1, and the finished product meets the requirements of nuclear power plant design technical indexes.

Preparing a test sample

The normal temperature-cured neutron shielding materials prepared in examples 1 to 5 were processed into different sizes, respectively, for testing the series of properties of the materials. The different performance test sample panels required the following: tensile strength (dumbbell-shaped bars, about 100mm long); hardness (50 mm. times.50 mm. times.6 mm); compressive strength (10 mm. times.10 mm. times.4 mm); thermal conductivity (11 mm. times.11 mm. times.1 mm); coefficient of thermal expansion (5 mm. times.5 mm); irradiation (200 mm. times.200 mm. times.100 mm).

② the test results are shown in Table 1

TABLE 1 test results of Material Properties

In summary, as can be seen from the test results of examples 1-5 in Table 1, the content of H element in the normal temperature-cured neutron shielding material of the present invention is about 5%, and the material density is greater than 1.10g/cm³The tensile strength is more than 0.34MPa, the Shore hardness is more than 55A, the compressive strength is more than 3.10MPa, the specific heat capacity is more than 0.8J/(g.K), and the heat conductivity coefficient is more than 0.5, so that the nuclear power design requirements are met. The expansion performance of the material under high temperature environment is measured, and the volume expansion coefficient is less than 6.5 to 10^-4cm³/cm³V. C, coefficient of linear thermal expansion < 1.9 x 10^-4cm³/cm³The temperature per DEG C is in a lower level, which shows that the material has better expansion resistance in a high-temperature environment, and the test result meets the design technical index requirements of the nuclear power station. The normal-temperature-cured neutron shielding material has excellent mechanical, thermal and irradiation resistance, can be cured at normal temperature and cast, can be operated at a high temperature of 300 ℃ for a long time, has a shielding rate of over 99% for thermal neutrons, has no change in neutron irradiation and gamma irradiation test results, completely meets the use requirements of shielding equipment in a containment vessel of a nuclear power station, and can realize industrial application.

The normal-temperature cured neutron shielding material is a high-performance neutron shielding material required by various radiation shielding devices in the containment vessel of the nuclear power station, so that the neutron shielding material which is good in neutron shielding effect and cured at the normal temperature is developed, and the performance of a finished product meets the technical index requirements of the nuclear power station.

The neutron shielding material adopts phenyl vinyl silicone oil as basic resin, and can generate hydrosilylation reaction with phenyl hydrogen-containing silicone oil at normal temperature under the conditions of platinum catalyst and vacuum reaction, so that the curing of the normal-temperature cured neutron shielding material at normal temperature is realized, the normal-temperature cured neutron shielding material can be directly constructed on site, and the construction performance of the material is greatly improved; meanwhile, as the Si-O and Si-H bonds have larger bond energy, the silicon resin system has good thermal stability, the integral high temperature resistance of the material is improved, and the long-term service temperature of the material reaches 300 ℃. The three raw materials of phenyl vinyl silicone oil, phenyl hydrogen silicone oil and magnesium hydroxide used in the normal-temperature cured neutron shielding material all contain a large amount of H element, the H element is an element with the best fast neutron moderating effect, and the material contains a large amount of H element, so that the normal-temperature cured neutron shielding material has excellent fast neutron moderating performance. The normal-temperature cured neutron shielding material is a high-performance neutron shielding material required by various radiation shielding devices in the containment vessel of the nuclear power station, so that the neutron shielding material which is good in neutron shielding effect and cured at the normal temperature is developed, and the performance of a finished product meets the technical index requirements of the nuclear power station.

In the description of the embodiments of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the illustrated orientations or positional relationships, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one logical division, and there may be other divisions when actually implemented, and for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed.

In light of the foregoing description of preferred embodiments in accordance with the invention, it is to be understood that numerous changes and modifications may be made by those skilled in the art without departing from the scope of the invention. The technical scope of the present invention is not limited to the contents of the specification, and must be determined according to the scope of the claims.