Patent Publication Number: US-2019168997-A1

Title: Elevator group management for occupant evacuation

Description:
BACKGROUND 
     The subject matter disclosed herein relates generally to the field of elevator systems, and specifically to a method and apparatus for coordinating the operation of multiple elevator cars. 
     Commonly, very tall buildings (ex: high rise or sky scrapers) require sky lobbies or transfer floors, which are intermediate interchange (i.e. transfer) floors where people may transfer from an elevator serving an upper portion of the building to an elevator serving a lower portion of the building. Some elevator systems can be operable during an emergency to evacuate occupants between an evacuation floor and a discharge floor. However, if travel between the evacuation floor and the discharge floor is impeded, occupants may have to use the stairs instead. 
     BRIEF DESCRIPTION 
     According to one embodiment, a method of operating a building elevator system includes determining that an evacuation call is active for an evacuation floor serviced by a first elevator group. A transfer floor serviced by the first elevator group is set as an evacuation discharge floor of the first elevator group. A second elevator group is requested to enter an evacuation mode of operation. The second elevator group is operable to service the transfer floor and a discharge floor. The transfer floor is set as the evacuation floor of the second elevator group. Control of the first elevator group and the second elevator group is coordinated to evacuate one or more occupants from the evacuation floor serviced by the first elevator group to the discharge floor serviced by the second elevator group. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the evacuation floor serviced by the first elevator group is unreachable by the second elevator group. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where requesting the second elevator group to enter the evacuation mode of operation is performed based on determining that the first elevator group is inhibited from traveling to the discharge floor. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where determining that the first elevator group is inhibited from traveling to the discharge floor is based on detecting a degraded hoistway condition. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include monitoring one or more conditions of the discharge floor, setting the evacuation discharge floor of the second elevator group to an alternate discharge floor based on detecting one or more degraded conditions at the discharge floor, and restricting travel of the second elevator group between the alternate discharge floor and the discharge floor. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include changing the evacuation discharge floor of one or more elevator cars of the first elevator group to a secondary transfer floor. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the evacuation mode of operation prioritizes travel between the transfer floor and the discharge floor over one or more requests received from one or more elevator call buttons between the transfer floor and the discharge. 
     According to another embodiment, control system of a building elevator system includes a processor and a memory including computer-executable instructions that, when executed by the processor, cause the processor to perform operations. The operations include determining that an evacuation call is active for an evacuation floor serviced by a first elevator group, setting a transfer floor serviced by the first elevator group as an evacuation discharge floor of the first elevator group, and requesting a second elevator group to enter an evacuation mode of operation, the second elevator group operable to service the transfer floor and a discharge floor. The operations also include setting the transfer floor as the evacuation floor of the second elevator group and coordinating control of the first elevator group and the second elevator group to evacuate one or more occupants from the evacuation floor serviced by the first elevator group to the discharge floor serviced by the second elevator group. 
     According to another embodiment, a computer program product is tangibly embodied on a computer readable medium. The computer program product includes instructions that, when executed by a processor, cause the processor to perform operations. The operations include determining that an evacuation call is active for an evacuation floor serviced by a first elevator group, setting a transfer floor serviced by the first elevator group as an evacuation discharge floor of the first elevator group, and requesting a second elevator group to enter an evacuation mode of operation, the second elevator group operable to service the transfer floor and a discharge floor. The operations also include setting the transfer floor as the evacuation floor of the second elevator group and coordinating control of the first elevator group and the second elevator group to evacuate one or more occupants from the evacuation floor serviced by the first elevator group to the discharge floor serviced by the second elevator group. 
     Technical effects of embodiments of the present disclosure include elevator group control for occupant evacuation. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  illustrates a schematic view of an elevator assembly, in accordance with an embodiment of the disclosure; 
         FIG. 2  illustrates a schematic view of a building elevator system, in accordance with an embodiment of the disclosure; 
         FIG. 3  illustrates a schematic view of a building elevator configuration, in accordance with an embodiment of the disclosure; 
         FIG. 4  illustrates a schematic view of a building elevator configuration, in accordance with an embodiment of the disclosure; and 
         FIG. 5  is a flow chart of method of operating a building elevator system, in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
       FIG. 1  shows a schematic view of an elevator assembly  10 , in accordance with an embodiment of the disclosure.  FIG. 2  shows schematic view of a building elevator system  100 , in accordance with an embodiment of the disclosure. With reference to  FIG. 1 , the elevator assembly  10  includes an elevator car  23  configured to move vertically upward and downward within a hoistway  50  along a plurality of car guide rails  60 . The elevator assembly  10  also includes a counterweight  28  operably connected to the elevator car  23  via a pulley system  26 . The counterweight  28  is configured to move vertically upward and downward within the hoistway  50 . The counterweight  28  moves in a direction generally opposite the movement of the elevator car  23 , as is known in conventional elevator assemblies. Movement of the counterweight  28  is guided by counterweight guide rails  70  mounted within the hoistway  50 . 
     The elevator assembly  10  also includes a power source  12 . The power is provided from the power source  12  to a switch panel  14 , which may include circuit breakers, meters, etc. From the switch panel  14 , the power may be provided directly to the drive unit  20  through the controller  30  or to an internal power source charger  16 , which converts alternating current (AC) power to direct current (DC) power to charge an internal power source  18  that requires charging. For instance, an internal power source  18  that requires charging may be a battery, capacitor, or any other type of power storage device known to one of ordinary skill in the art. Alternatively, the internal power source  18  may not require charging from the external power source  12  and may be a device such as, for example a gas powered generator, solar cells, hydroelectric generator, wind turbine generator or similar power generation device. The internal power source  18  may power various components of the elevator assembly  10  when an external power source is unavailable. The drive unit  20  drives a machine  22  to impart motion to the elevator car  23  via a traction sheave of the machine  22 . The machine  22  also includes a brake  24  that can be activated to stop the machine  22  and elevator car  23 . As will be appreciated by those of skill in the art,  FIG. 1  depicts a machine room-less elevator assembly  10 , however the embodiments disclosed herein may be incorporated with other elevator assemblies that are not machine room-less or that include any other known elevator configuration. In addition, hydraulic elevator systems, elevator systems having more than one independently operating elevator car in each elevator shaft and/or ropeless elevator systems may also be used. In one embodiment, the elevator car may have two or more compartments. 
     The controller  30  is responsible for controlling the operation of the elevator assembly  10 . The controller  30  is tied to a control system  110  ( FIG. 2 ), which is responsible for controlling multiple elevator assemblies and will be discussed below. The controller  30  may also determine a mode (motoring, regenerative, near balance) of the elevator car  23 . The controller  30  may use the car direction and the weight distribution between the elevator car  23  and the counterweight  28  to determine the mode of the elevator car  23 . The controller  30  may adjust the velocity of the elevator car  23  to reach a target floor. The controller  30  may include a processor and an associated memory. The processor may be, but is not limited to, a single-processor or multi-processor system of any of a wide array of possible architectures, including field programmable gate array (FPGA), central processing unit (CPU), application specific integrated circuits (ASIC), digital signal processor (DSP) or graphics processing unit (GPU) hardware arranged homogenously or heterogeneously. The memory may be but is not limited to a random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic or any other computer readable medium. 
     As seen in  FIG. 2 , a building elevator system  100  within a building  102  may include multiple different individual elevator assemblies  10   a - 10   f.  The elevator assemblies  10  may be divided up into two or more elevator groups  92   a,    92   b.  In very tall buildings (ex: high rise and skyscrapers) with a large number of floors  80   a - 80   f,  multiple elevator groups  92   a,    92   b  may be used to get occupants to desired destinations faster and more efficiently. Multiple elevator groups  92   a,    92   b  may also exist in shorter buildings for various other reasons including but not limited to, efficiency and/or structural constraints.  FIG. 2  includes a first elevator group  92   a  and a second elevator group  92   b.  Floor coverage of each elevator group  92   a,    92   b  typically overlaps at a transfer floor  104  (ex: sky lobby), so that occupants may disembark one of the elevator groups  92   a,    92   b  and enter another. Buildings may have multiple transfer floors  104  including a first transfer floor  104   a  and a second transfer floor  104   b  ( FIG. 4 ). As seen in  FIG. 2 , the floor coverage of the first elevator group  92   a  overlaps the floor coverage of the second elevator group  92   b  at floor  80   d,  which is considered the transfer floor  104 . Each elevator group  92   a,    92   b  may have one or more elevator assemblies  10   a - 10   f  having elevator cars  23   a - 23   f  in an elevator hoistway  50   a - 50   d.  In an embodiment, the first elevator group  92   a  is at a higher elevation than the second elevator group  92   b  in the building  102 . That is, the first elevator group  92   a  serves floors  80   d - 80   f  and the second elevator group  92   b  serves floors  80   a - 80   d.  In order for a passenger from floors  80   a - 80   c  to reach floors  80   e - 80   f,  they would need to transfer from second elevator group  92   b  to first elevator group  92   a  at floor  80   d.  While the building  102  of  FIG. 2  is depicted with six floors, buildings may have any desired number of floors. Moreover, the second elevator group  92   b  and first elevator group  92   a  may each serve any number of independent and overlapping floors as desired. 
     Each floor  80   a - 80   f  in the building  102  of  FIG. 2  may have an elevator call button  89   a - 89   f  and an evacuation alarm  88   a - 88   f  The elevator call button  89   a - 89   f  sends an elevator call to the control system  110 . The elevator call button  89   a - 89   f  may be a push button and/or a touch screen and may be activated manually or automatically. For example, the elevator call button  89   a - 89   f  may be activated by a building occupant pushing the elevator call button  89   a - 89   f  The elevator call button  89   a - 89   f  may also be activated by voice recognition or a passenger detection mechanism in the hallway, such as, for example a weight sensing device, a visual recognition device, and a laser detection device. The evacuation alarm  88   a - 88   f  may be activated or deactivated either manually or automatically through an alarm system (not depicted) operable to alert building occupants of conditions and threats relevant to elevator operation (e.g., fire, chemical, biological agents or smoke near points of elevator entry/egress). If the evacuation alarm  88   a - 88   f  is activated, an evacuation call is sent to the control system  110  indicating the respective floor  80   a - 80   f  where the evacuation alarm  88   a - 88   f  was activated. In the example of  FIG. 2 , an evacuation alarm  88   f  is activated, and floor  80   f  is the evacuation floor  105 . 
     In building  102  having a second elevator group  92   b  and a first elevator group  92   a,  in the case of an evacuation, elevator cars  23   a - 23   c  of the first elevator group  92   a  may carry occupants to the transfer floor  104  for evacuation, and the control system  110  may send elevator cars  23   d - 23   f  of the second elevator group  92   b  to the transfer floor  104  to receive the occupants exiting the elevator cars  23   a - 23   c  of the first elevator group  92   a  and, thereby, return them to a discharge floor  106 , e.g., the ground floor (or any other desired evacuation floor) for evacuation. In the example of  FIG. 2 , the discharge floor  106  may be floor  80   a,  such as a lobby of building  102 . In one embodiment, the discharge floor  106  may be any desired floor that allows people to evacuate the building or otherwise offers people safety (e.g., a floor with a refuge space). 
     The control system  110  is operably connected to the controller  30  (see  FIG. 1 ) of each elevator assembly  10 . The control system  110  is configured to the control and coordinate operation of multiple elevator groups  92   a,    92   b.  The control system  110  may be an electronic controller including a processor and an associated memory comprising computer-executable instructions that, when executed by the processor, cause the processor to perform various operations. The processor may be, but is not limited to, a single-processor or multi-processor system of any of a wide array of possible architectures, including field programmable gate array (FPGA), central processing unit (CPU), application specific integrated circuits (ASIC), digital signal processor (DSP) or graphics processing unit (GPU) hardware arranged homogenously or heterogeneously. The memory may be but is not limited to a random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic or any other computer readable medium. 
     The elevator groups  92   a,    92   b  may also include a notification device  74  as seen in  FIG. 1 , and each elevator group  92   a,    92   b  may include a notification device  74   a - 74   f  as seen in  FIG. 2 . The notification device  74   a - 74   f  may be located within the individual elevator cars  23   a - 23   f,  at each floor  80   a - f,  and/or on the transfer floor  104 . The notification device  74   a - 74   f  is in operative communication with the control system  110 . The notification device  74   a - 74   f  can be configured to provide transfer instructions to occupants. For example, the transfer instructions may describe where on the transfer floor  104  to board an elevator car  23   d - 23   f  of the second elevator group  92   b  when the occupants are disembarking an elevator car  23   a - 23   c  of the first elevator group  92   a.  The notification device  74   a - 74   f  may provide transfer instructions in audible and/or visual form. 
     The elevator assemblies  10   a - 10   f  may also include a sensor system  76  configured to detect a number of occupants in a particular elevator car  23 , as seen in  FIG. 1 . The sensor system  76  is also seen in  FIG. 2 , as sensor systems  76   a - 76   f  The sensor system  76  is in operative communication with the control system  110 . The sensor system  76  may use a variety of sensing mechanisms such as, for example, a visual detection device, a weight detection device, a laser detection device, a door reversal monitoring device, a thermal image detection device, and a depth detection device. The visual detection device may be a camera that utilizes visual recognition to identify and count individual passengers. The weight detection device may be a scale to sense the amount of weight in an elevator car  23  and then determine the number of passengers from the weight sensed in combination with one or more other sensing mechanisms, such as a door detector. The laser detection device may detect how many passengers walk through a laser beam to determine the number of passengers in the elevator car  23 . Similarly, a door reversal monitoring device also detects passengers entering the car so as not to close the elevator door on a passenger and thus may be used to determine the number of passengers in the elevator car  23 . The thermal detection device may be an infrared or other heat sensing camera that utilizes detected temperature to identify and count individual passengers in combination with other image-based detection for headcounts, facial detection, and/or other sensing techniques. The depth detection device may be a 2-D, 3-D or other depth/distance detecting camera that utilizes detected distance to an object to identify and count individual passengers. As may be appreciated by one of skill in the art, in addition to the stated methods, additional methods may exist to sense the number of passengers and one or any combination of these methods may be used to determine the number of passengers in the elevator car. In addition or in place of counting the number of occupants, the control system  110  may detect the amount of free and/or occupied space in the elevator car  23  and use this data instead of passenger count. In some embodiments, the control system  110  may estimate the number of occupants based upon the amount of free and/or occupied space (along with weight data) in the elevator car  23 . 
     Determining the number of occupants in an elevator car  23   a - 23   c  of the first elevator group  92   a  approaching the transfer floor may help the control system  110  determine how many elevators cars  23   d - 23   f  to send to the transfer floor  104  from the second elevator group  92   b.  The control system  110  is configured to determine the number of occupants in an elevator car  23   a - 23   c  of the first elevator group  92   a  so as to send the appropriate number of elevators cars  23   d - 23   f  from the second elevator group  92   b  to the transfer floor  104 , which can expedite transferring passengers between the two elevator groups  92   a,    92   b.    
     In embodiments, the control system  110  can determine one or more conditions of the building  102  to assist in determining whether travel of elevator cars  23   a - 23   c  of the first elevator group  92   a  can reach a desired floor. For example, the control system  110  can monitor a building sway sensor  112 , a wind sensor  114 , and/or other environmental sensors. The sway sensor  112  can monitor motion magnitude and/or frequency of motion of the building  102 , for instance due to seismic activity or wind. The wind sensor  114  may assist in quantifying the source of motion of the building  102  and the intensity level of a building sway event. The sway sensor  112  may be accelerometer based, pendulum based, or optically based, for example, to determine the magnitude and frequency of movement of a portion of the building  102 . 
     In some embodiments, the first elevator group  92   a  is an express elevator system that is accessible from the discharge floor  106  under normal operating conditions, as depicted in the example building elevator configuration  200  of  FIG. 3  and the building elevator configuration  250  of  FIG. 4 . The building elevator configuration  200  includes an inaccessible region of floors  204  that prevent entrance/egress in the elevators of the first elevator group  92   a  at floors between the discharge floor  106  and the transfer floor  104 . The building elevator configuration  250  includes a first region of inaccessible floors  204   a  that prevents entrance/egress in the elevators of the first elevator group  92   a  at floors between a first transfer floor  104   a  (e.g., equivalent to the transfer floor  104  of  FIG. 3 ) and a second transfer floor  104   b,  and a second region of inaccessible floors  204   b  that prevents entrance/egress in the elevators of the first elevator group  92   a  at floors between the second transfer floor  104   b  and the discharge floor  106 . It will be understood that numerous other elevator groupings and configurations are contemplated. In the example of  FIG. 4 , occupant transfers between the first elevator group  92   a  and the second elevator group  92   b  can occur at either the first transfer floor  104   a  or the second transfer floor  104   b.  The second elevator group  92   b  may also support an alternate discharge floor  210  that, for instance, may have access to outside of the building  102 , such as through a stairway, an escalator system, a sky bridge, or other such structure. The alternate discharge floor  210  may be preferred if there is an evacuation alarm  88   a  active or other such degraded condition detected at the discharge floor  106 . The alternate discharge floor  210  may be selected based on environmental or other current conditions such that the alternate discharge floor is selected for use as needed. Notably, in the example of  FIG. 4 , the alternate discharge floor  210  is inaccessible from the first elevator group  92   a  due to alignment with the second region of inaccessible floors  204 . 
     When the second elevator group  92   b  is configured in an evacuation mode of operation to support evacuation through the first elevator group  92   a,  the transfer floor  104  becomes an evacuation discharge floor  206  of the first elevator group  92   a  and an evacuation floor  205  of the second elevator group  92   b.  Such an event could put the second elevator group  92   b  into evacuation even if it was not in evacuation initially. Similarly, if multiple transfer floors  104   a,    104   b  are supported, when the second elevator group  92   b  is configured in an evacuation mode of operation to support evacuation through the first elevator group  92   a,  the first transfer floor  104   a  can be a first evacuation discharge floor  206   a  of the first elevator group  92   a  and a first evacuation floor  205   a  of the second elevator group  92   b.  Similarly, the second transfer floor  104   b  can be a second evacuation discharge floor  206   b  of the first elevator group  92   a  and a second evacuation floor  205   b  of the second elevator group  92   b.    
     Referring now to  FIG. 5 , while referencing components of  FIGS. 1-4 ,  FIG. 5  shows a flow chart of method  300  of operating a building elevator system  100 , in accordance with an embodiment of the disclosure which may be used for various configurations, such as building elevator configurations  200 ,  250 . The method  300  can include additional steps beyond those depicted in  FIG. 5  and some steps may be performed in an alternate order. 
     At block  302 , the building elevator system  100  is under normal operation. Under normal operation, the control system  110  controls the first elevator group  92   a  and the second elevator group  92   b  according to normal dispatching priorities (e.g., non-evacuation mode). As mentioned above, the floor coverage of the first elevator group  92   a  overlaps the floor coverage of the second elevator group  92   b  by at least one transfer floor  104 , as seen in  FIG. 2 . In the example of  FIG. 2 , the transfer floor  104  is floor  80   d.  In the example of  FIG. 4 , there are multiple transfer floors  104 , including a first transfer floor  104   a  and a second transfer floor  104   b,  in some configurations, such as the building elevator configuration  250 . 
     At block  304 , the control system  110  detects if an evacuation call has been received. At block  304 , based determining that an evacuation call is active for an evacuation floor  105  serviced by a first elevator group  92   a,  the method  300  continues to block  306 ; otherwise, the method  300  returns to block  302 . At block  306 , the control system  110  sets a transfer floor  104  serviced by the first elevator group  92   a  as an evacuation discharge floor  206  of the first elevator group  92   a.    
     At block  308 , the control system  110  requests a second elevator group  92   b  to enter an evacuation mode of operation, where the second elevator group  92   b  is operable to service the transfer floor  104  and a discharge floor  106 . Requesting the second elevator group  92   b  to enter the evacuation mode of operation can be performed based on determining that the first elevator group  92   a  is inhibited from traveling to the discharge floor  106 , for instance, based on a degraded hoistway condition. For example, the control system  110  can detect a sway condition of the first elevator group  92   a,  compare the sway condition to a sway limit, and determine that the first elevator group  92   a  is inhibited from traveling between the transfer floor  104  and the discharge floor  106  based on a result of comparing the sway condition to the sway limit. The sway limit can be defined in terms of a sway frequency and/or magnitude. For instance, if the resonant frequency of the first elevator group  92   a  would result in a risk of component contact as elevator cars  23   a - 23   c  traverse between the evacuation floor  105  and the discharge floor  106 , then direct travel to the discharge floor  106  can be inhibited, resulting in a mode transition for the second elevator group  92   b  to enter the evacuation mode of operation even though no floors  80   a - 80   d  directly serviced by the second elevator group  92   b  have a corresponding evacuation call. Other examples include detected seismic activity responsive to a seismic sensor, a counterweight misalignment condition, and other such conditions. The evacuation mode of operation can prioritize travel between the transfer floor  104  and the discharge floor  106  over one or more requests received from one or more elevator call buttons  89   b - 89   c  between the transfer floor  104  and the discharge floor  106 . For example, rather than servicing elevator call requests between the transfer floor  104  and discharge floor  106 , the control system  110  stops at the transfer floor  104  or the discharge floor  106  while evacuation is active. 
     At block  310 , the control system  110  sets the transfer floor  104  as the evacuation floor  205  of the second elevator group  92   b.  The evacuation floor  105  serviced by the first elevator group  92   a  may be unreachable by the second elevator group  92   b.  At block  312 , the control system  110  coordinates control of the first elevator group  92   a  and the second elevator group  92   b  to evacuate one or more occupants from the evacuation floor  104  serviced by the first elevator group  92   a  to the discharge floor  106  serviced by the second elevator group  92   b.    
     In embodiments, the control system  110  can monitor one or more conditions of the discharge floor  106 . For example, the discharge floor  106  can be monitored for fire, flooding, and/or other hazards using various sensors and detection techniques. The control system  110  can set the evacuation discharge floor of the second elevator group  92   b  to an alternate discharge floor  210  based on detecting one or more degraded conditions at the discharge floor  106 . The alternate discharge floor  210  may have an alternate exit from the building  102 . The control system  110  can restrict travel of the second elevator group  92   b  between the alternate discharge floor  210  and the discharge floor  106 , for instance, to prevent the degraded conditions from spreading to the alternate discharge floor  210 . Further, the multiple transfer floors  104   a,    104   b  can enable changing the first evacuation discharge floor  206   a  of one or more elevator cars  23   a - 23   c  of the first elevator group  92   a  to a second evacuation discharge floor  206   b  at a secondary transfer floor  104   b    
     While the above description has described the flow process of  FIG. 5  in a particular order, it should be appreciated that unless otherwise specifically required in the attached claims that the ordering of the steps may be varied. 
     As described above, embodiments can be in the form of processor-implemented processes and devices for practicing those processes, such as a processor. Embodiments can also be in the form of computer program code containing instructions embodied in tangible media (i.e., a computer program product), such as network cloud storage, SD cards, flash drives, floppy diskettes, CD ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes a device for practicing the embodiments. Embodiments can also be in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into an executed by a computer, the computer becomes an device for practicing the embodiments. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.