Patent Publication Number: US-9845920-B2

Title: Defroster for oxygen liquefier

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the priority benefit under 35 U.S.C. §371 of international patent application no. PCT/IB2012/05115, filed Mar. 9, 2012, which claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/452,206 filed on Mar. 14, 2011, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure pertains to defrosting a component of an oxygen liquefier, and, in particular, defrosting an oxygen line in an oxygen concentrator and liquefier system to remove a whole or partial blockage caused by frozen liquid, such as water, within the oxygen line. 
     2. Description of the Related Art 
     It is well known to liquefy oxygen and other gases. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require pressurization as well. Some gas liquefiers typically rely on the absence of moisture in the gas to be liquefied. Some of the standard techniques used to remove moisture include the use of membranes, adsorption, absorption, and/or cryogenic distillation. 
     However, oxygen coming directly from a standard pressure swing adsorption (PSA) system used as an oxygen concentrator may still contain trace amounts of moisture. In some instances, for example, the trace amounts of moisture may have a dew point of approximately −60° C. As a result, ice may form within gas lines during liquefaction of oxygen coming from a PSA system, thus restricting or blocking oxygen flow and/or acting as an insulator reducing heat exchange efficiency. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an aspect of one or more embodiments to provide a method for operating an oxygen concentrator and liquefier system. The method includes extracting oxygen from air obtained from an ambient environment using one or more sieve beds. The method includes transferring oxygen extracted at the one or more sieve beds to a liquid oxygen reservoir via an oxygen line. The oxygen extracted at the one or more sieve beds is liquefied between the one or more sieve beds and the liquid oxygen reservoir. The method includes defrosting the oxygen line to melt frozen liquid within the oxygen line. 
     It is yet another aspect of one or more embodiments to provide an oxygen concentrator and liquefier system configured to defrost one or more oxygen lines included therein. The system includes one or more sieve beds, a liquid oxygen reservoir, an oxygen line, and a heating apparatus. The one or more sieve beds are configured to extract oxygen from air obtained from an ambient environment. The liquid oxygen reservoir is configured to store oxygen extracted at the one or more sieve beds that has been liquefied. The oxygen line is configured to provide fluid communication between the one or more sieve beds and the liquid oxygen reservoir. The heating apparatus is configured to defrost the oxygen line to melt frozen liquid within the oxygen line. 
     It is yet another aspect of one or more embodiments to provide an oxygen concentrator and liquefier system configured to defrost oxygen communication means included therein. The system includes extraction means, storage means, oxygen communication means, and heating means. The extraction means is for extracting oxygen from air obtained from an ambient environment. The storage means is storing oxygen extracted at the extraction means that has been liquefied. The oxygen communication means is for providing fluid communication between the extraction means and the storage means. The heating means is for defrosting the oxygen communication means to melt frozen liquid within the oxygen communication means. 
     These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a system configured for oxygen concentration and liquefaction, in accordance with one or more embodiments; 
         FIG. 2  illustrates exemplary embodiments of a multi-conduit tube section; and 
         FIG. 3  illustrates a method for defrosting an oxygen line in an oxygen liquefier coupled to an oxygen concentrator, in accordance with one or more embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
     As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
       FIG. 1  is a block diagram illustrating a system  100  configured for oxygen concentration and liquefaction, in accordance with one or more embodiments. As depicted in  FIG. 1 , system  100  includes a user interface  102 , a controller  104 , an oxygen concentrator  106 , an oxygen liquefier  108 , and/or other components. The description of system  100  is illustrative and not intended to be limiting. For example, system  100  may include additional components not necessary to describe the present technology. Additionally, while the present technology is describe in the context of an oxygen concentration and liquefaction system, the concepts can be applied to other types of gas liquefaction systems (e.g., a nitrogen liquefaction system). 
     User interface  102  is configured to provide an interface between system  100  and a user through which the user may provide information to and receive information from system  100 . This enables data, results, and/or instructions and any other communicable items, collectively referred to as “information,” to be communicated between the user and system  100 . As used herein, the term “user” can refer to a single individual or a group of individuals who may be working in coordination. Examples of interface devices suitable for inclusion in user interface  102  include a keypad, buttons, switches, a keyboard, knobs, levers, a display screen, a touch screen, speakers, a microphone, an indicator light, an audible alarm, and a printer. In one embodiment, user interface  102  actually includes a plurality of separate interfaces. 
     It is to be understood that other communication techniques, either hard-wired or wireless, are also contemplated as user interface  102 . For example, user interface  102  may be integrated with a removable storage interface provided by electronic storage. In this example, information may be loaded into system  100  from removable storage (e.g., a smart card, a flash drive, a removable disk, etc.) that enables the user(s) to customize the implementation of system  100 . Other exemplary input devices and techniques adapted for use with system  100  as user interface  102  include, but are not limited to, an RS-232 port, RF link, an IR link, modem (telephone, cable or other). In short, any technique for communicating information with system  100  is contemplated for user interface  102 . 
     Controller  104  is configured to provide information processing capabilities in system  100 . Controller  104  may be communicatively coupled with one or more components of system  100 . Controller  104  may be configured to control the operation of one or more components of system  100  and/or the coordination therebetween. As such, controller  104  may include one or more of a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information. In some embodiments, controller  104  includes and/or is communicatively coupled to electronic storage media configured to store instructions executable by controller  104 . Although controller  104  is shown in  FIG. 1  as a single entity, this is for illustrative purposes only. In some implementations, controller  104  may include a plurality of processing units. These processing units may be physically located within the same device or computing platform, or controller  104  may represent processing functionality of a plurality of devices operating in coordination. 
     Oxygen concentrator  106  is configured to generate gas having an elevated oxygen content (e.g., 93% pure medical grade oxygen) from ambient air (approximately 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and small amounts of other gases), gas from a gas cylinder, and/or any other gas source. In the embodiment depicted in  FIG. 1 , oxygen concentrator  106  includes a gas compressor  110 , a valve  112 , one or more pressure swing adsorption (PSA) sieve beds  114 , a moisture removal stage  116 , and/or other components. The description of oxygen concentrator  106  is illustrative and not intended to be limiting. For example, oxygen concentrator  106  may include additional components not necessary to describe the present technology, such a product thanks, pressure relieve valves, and filters. Additionally, while the present technology is describe in the context of a pressure swing adsorption system, the concepts can be applied to other types of gas concentrators, such as ceramic and distillation type of oxygen generation systems. 
     Compressor  110  is configured to provide gas at an elevated pressure relative to atmosphere. The gas (e.g., air) is obtained by gas compressor  110  from a gas source (e.g., ambient environment). Gas is introduced to gas compressor  110  via an air intake line  118 . Gas compressor  110  provides pressurized gas via a primary air line  120 . By way of non-limiting example, gas compressor  110  may include one or more of a piston-type compressor, a rotary screw compressor, a vane compressor, a centrifugal compressor, and/or other devices configured to provide gas at an elevated pressure relative to atmosphere. According to some embodiments, pressurized gas provided by gas compressor  110  has an elevated temperature, relative to gas obtained via air intake line  118 , due to gas compression performed by gas compressor  110 . For example, pressurized gas provided by gas compressor  110  may have a temperature of approximately 80° C. to 90° C., depending on the temperature of gas obtained via air intake line  118 . 
     Valve  112  is configured to wholly or partially redirect received gas between two or more components of system  100 . As depicted in  FIG. 1 , valve  112  receives pressurized gas from gas compressor  110  via primary air line  120 . During normal operation, i.e., generation of gas having high oxygen content, valve  112  directs pressurized gas to PSA sieve beds  114  via at least one sieve bed air line  122 . While defrosting one or more gas lines of system  100 , valve  112  directs pressurized gas to a defroster air line  124 . By way of non-limiting example, valve  112  may be controlled by hydraulic, pneumatic, manual, solenoid, motor, and/or other techniques suitable for controlling valve  112  to redirect gas. In some embodiments, controller  104  directs valve  112  to redirect gas. Such redirection may be responsive to detection of a whole or partial blockage of a gas line included in system  100 . 
     PSA sieve beds  114  are configured to separate one or more gas species from a mixture of gases under pressure received via sieve bed air line  122 . The one or more gas species may be separated according to the one or more species&#39; molecular characteristics and affinity for an adsorbent material. Adsorptive materials (e.g., activated carbon, silica gel, alumina, zeolite, and/or other suitable materials) are used as a molecular sieve to adsorb the one or more gas species at an elevated pressure. Adsorbent materials for PSA systems are generally very porous materials chosen because of their large surface areas. After the adsorptive material is wholly or partially saturated with the one or more gas species, the process swings to low pressure to release or desorb the one or more species from the adsorbent material. One or more gas species separated from the mixture of gases are outputted via an oxygen line  126 . 
     To illustrate, pressurized air received via sieve bed air line  122  can be passed through a PSA sieve bed containing an adsorbent bed that attracts nitrogen more strongly than it does oxygen. Part or all of the nitrogen will be adsorbed in the PSA sieve bed, and the gas coming out of the PSA sieve bed will be enriched in oxygen. When the sieve bed reaches the end of its capacity to adsorb nitrogen, it can be regenerated by reducing the pressure, thereby releasing the adsorbed nitrogen. It is then ready for another cycle of producing enriched oxygen. Using two PSA sieve beds allows near-continuous production of a target gas. Such use may also permits so-called pressure equalization, where the gas leaving a first PSA sieve bed being depressurized is used to partially pressurize a second PSA sieve bed. 
     Moisture removal stage  116  is configured to remove moisture from gas received from PSA sieve beds  114  via oxygen line  126 , in accordance with some embodiments. In some embodiments, for cost efficiency and/or other purposes, no further conditioning of gas coming from PSA sieve beds  114  is performed to remove moisture. As such, in some embodiments, moisture removal stage  116  is omitted from system  100 . Moisture removal stage  116  may utilize one or more techniques to remove moisture including membranes, adsorption, absorption, and/or other techniques suitable for removing moisture from gas. 
     Oxygen liquefier  108  is configured to generate liquefied oxygen from gaseous oxygen. Gaseous oxygen is received from oxygen concentrator  106  via oxygen line  126 . Liquefied oxygen may be generated from gaseous oxygen by reducing the temperature of the gaseous oxygen (e.g., to cryogenic levels) and/or by pressurizing the gaseous oxygen. In the embodiment depicted in  FIG. 1 , oxygen liquefier  108  includes a heat exchanger  128  and a liquid oxygen reservoir  130  contained within an environmental isolation apparatus  132 , a refrigeration system  134 , a temperature sensor  136 , a flow sensor  138 , and/or other components. The description of oxygen liquefier  108  is illustrative and not intended to be limiting. For example, oxygen liquefier  108  may include additional components not necessary to describe the present technology. Additionally, the concepts disclosed herein may be applied to other types of gas liquefiers. 
     Heat exchanger  128  is configured to transfer heat from one medium to another. Such heat transfer may serve to liquefy gas carried by oxygen line  126  and/or to melt frozen liquid, such as water, within oxygen line  126 . According to one or more embodiments, oxygen line  126  is placed in thermal contact with defroster air line  124 , a refrigerant line  140 , and/or one or more other lines configured to carry fluid. Refrigerant line  140  is configured to draw heat away from oxygen line  126 , and is described in further detail in connection with refrigeration system  134 . 
     Defroster air line  124  is configured to provide heat to oxygen line  126 . Thermal contact between oxygen line  126 , defroster air line  124 , and/or refrigerant line  140  may be achieved in a number of configurations. For example, oxygen line  126 , defroster air line  124 , and/or refrigerant line  140  may be joined together in a collinear configuration, such as by soldering. As another example, oxygen line  126 , defroster air line  124 , and/or refrigerant line  140  may be combined as a single component, such as a multi-conduit tube, thus providing thermal contact therebetween. Exemplary embodiments of a multi-conduit tube section, which may include one or more of oxygen line  126 , defroster air line  124 , refrigerant line  140 , and/or other lines, is described in further detail in connection with  FIG. 2 . 
     According to some embodiments, the thermal contact between defroster air line  124  and oxygen line  126  extends over the entire length of heat exchanger  128  or over a portion of heat exchanger  128 . In some embodiments, the thermal contact between defroster air line  124  and oxygen line  126  begins proximate to a point along oxygen line  126  where a temperature of oxygen line  126  is determined to be less than a dew point of oxygen within oxygen line  126  and ends at a downstream point along oxygen line  126 . 
     It is noteworthy that, in some embodiments, heat exchanger  128  implements other techniques for transferring heat to and from oxygen line  126 . In some embodiments, for example, heat is provided to oxygen line  126  by an electric heating coil or rod. A gel or other fluid is flowed over oxygen line  126 , in some embodiments, to provide heat to or draw heat from oxygen line  126 . The examples provided herein with respect to heat exchanger  128  are not intended to be limiting as other approaches and techniques are contemplated for transferring heat to and from oxygen line  126 . 
     Once frozen liquid, such as water, within oxygen line  126  has been melted, the resulting liquid can be removed. In various embodiments, liquid (i.e., water) may be drained by gravity, purged by flowing gas through oxygen line  126 , evaporated, and/or removed using other techniques suitable for discharging liquid water from oxygen line  126 . 
     Liquid oxygen reservoir  130  is configured to store liquefied gas. In some embodiments, oxygen enriched gas produced by oxygen concentrator  106  and liquefied by oxygen liquefier  108  is stored by liquid oxygen reservoir  130 . The liquefied gas stored by liquid oxygen reservoir  130  may be retrieved and used for various purposes, such as, for example, medical applications. Liquid oxygen reservoir  130  may include a vacuum flask or dewar, and/or other container suitable for storing materials at cryogenic temperatures. 
     Environmental isolation apparatus  132  is configured to thermally isolate heat exchanger  128 , liquid oxygen reservoir  130 , and/or other components from an ambient environment. According to some embodiments, environmental isolation apparatus  132  may include a vacuum or partially evacuated volume configured to house heat exchanger  128 , liquid oxygen reservoir  130 , and/or other components. 
     Refrigeration system  134  is configured to cool a refrigerant and circulate that refrigerant through heat exchanger  128  in order to draw heat away from oxygen line  126 . Drawing heat away from oxygen line  126  is performed to liquefy gas carried by oxygen line  126 . Refrigeration system  134  may include a refrigeration compressor (not depicted) configured to drive circulation of the refrigerant. Refrigeration system  134  may include various other components (not depicted) configured to cool or otherwise treat the refrigerant such as, for example, one or more of a condenser coil, a fan, a hot separator, a cold separator, a filter, a dryer, and/or other components for cooling or otherwise treating the refrigerant. Cooled refrigerant may be delivered from refrigeration system  134  to heat exchanger  128  via refrigerant line  140 , while spent refrigerant may be returned from heat exchanger  128  to refrigeration system  134  via refrigerant line  140 . 
     Temperature sensor  136  is configured generate a signal that can be used to determine temperature. In some embodiments, temperature sensor  136  is used in conjunction with controller  104  to determine a temperature at a specific point within heat exchanger  128 . Temperature sensor  136  may be utilized to determine when a temperature at some position along oxygen line  126  falls below the dew point of gas carried by oxygen line  126 . Such a determination may be utilized by controller  104  as a basis to effectuate a change an operation state of system  100  from oxygen concentration and liquefaction to defrosting of oxygen line  126 , and vice versa. Although depicted as a single element in  FIG. 1 , temperature sensor  136  may represent one or more temperature sensors positioned at one or more locations throughout system  100 . By way of non-limiting example, temperature sensor  136  may include a thermistor, thermometer, and/or other device configured to determine temperature. 
     Flow sensor  138  is configured generate a signal that can be used to determine a flow rate of fluid through a conduit. In some embodiments, flow sensor  138  is used in conjunction with controller  104  to determine a flow rate of liquefied or gaseous oxygen though oxygen line  126 . Such a determination may be made by monitoring a pressure within oxygen line  126 . A flow rate may be utilized by controller  104  as a basis to effectuate a change an operation state of system  100  from oxygen concentration and liquefaction to defrosting of oxygen line  126 , and vice versa. In accordance with some embodiments, a whole or partial blockage of oxygen line  126  by frozen water ultimately leads to an increase in pressure within oxygen line  126 , but initially it leads to a decrease in pressure. Such a decrease in pressure may be utilized to trigger controller  104  to change an operational state of system  100 . Although depicted as a single element in  FIG. 1 , flow sensor  138  may represent one or more flow sensors positioned at one or more locations throughout system  100 . By way of non-limiting example, flow sensor  138  may include a pressure sensor, a rotary potentiometer, a velocimeter, a vane meter sensor, a hot wire sensor, a cold wire sensor, a Kármán vortex sensor, a membrane sensor, laminar flow elements, and/or other device configured to determine a fluid flow rate. 
     According to some embodiments, oxygen line  126  is defrosted for a predetermined length of time. After this period, oxygen liquefier  108  may resume liquefaction of oxygen received by oxygen line  126 . In some embodiments, there is a pause between defrosting and liquefaction. If, after a defrost cycle has been performed, a blockage is detected, system  100  may initiate another defrost cycle. In some embodiments, a defrost routine is terminated based on a temperature of oxygen line  126  (or other component of heat exchanger  128 ) as determined in conjunction with temperature sensor  136 . 
     In some embodiments (not depicted in  FIG. 1 ), valve  112  is positioned between PSA sieve beds  114  and oxygen liquefier  108 . In such embodiments, valve  112  is configured to wholly or partially redirect oxygen outputted by PSA sieve beds  114  to defroster air line  124 . The redirected oxygen carried by the defroster air line  124  can then used to provide heat to the oxygen line  126  within the heat exchanger  128 . A heater (not depicted) may be included in system  100  to heat a gas carried by defroster air line  124 , in accordance with some embodiments. 
       FIG. 2  illustrates exemplary embodiments of a multi-conduit tube section. More specifically, a multi-conduit tube section  202 , a multi-conduit tube section  204 , a multi-conduit tube section  206 , a multi-conduit tube section  208 , and/or other multi-conduit tube sections configured to carry two or more fluids may be included in heat exchanger  128  (see  FIG. 1 ) to facilitate thermal transfer between defroster air line  124 , oxygen line  126 , refrigerant line  140 , and/or other lines. The description of multi-conduit tube sections  202 ,  204 ,  206 , and/or  208  is illustrative and not intended to be limiting. For example, although multi-conduit tube sections  202 ,  204 ,  206 , and/or  208  are depicted in  FIG. 2  as having two conduits, multi-conduit tube sections  202 ,  204 ,  206 , and/or  208  may include two or more conduits. 
     Multi-conduit tube section  202  is illustrative of defroster air line  124  and oxygen line  126  being joined together to form a thermal contact therebetween. Such joining may be achieved by soldering and/or other techniques suitable for joining gas lines. Multi-conduit tube section  204  is illustrative of defroster air line  124  and oxygen line  126  being formed as a single component with a rectangular profile. Multi-conduit tube section  206  is illustrative of defroster air line  124  and oxygen line  126  being formed as a single component with a oval profile. Multi-conduit tube section  208  is illustrative of a coaxial configuration where the inner conduit is defroster air line  124  or oxygen line  126 , and the outer conduit is the other. 
       FIG. 3  illustrates a method  300  for defrosting an oxygen line in an oxygen liquefier coupled to an oxygen concentrator, in accordance with one or more embodiment. The operations of the method  300  presented below are intended to be illustrative. In some implementations, the method  300  may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of the method  300  are illustrated in  FIG. 3  and described below is not intended to be limiting. 
     In some implementations, the method  300  may be implemented in and/or by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing and/or effectuating some or all of the operations of the method  300  in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of the method  300 . 
     At operation  302 , oxygen is extracted from air obtained from an ambient environment using one or more sieve beds. According to some embodiments, oxygen concentrator  106  and/or components therein perform operation  302 . 
     At operation  304 , oxygen extracted at the one or more sieve beds is transferred to a liquid oxygen reservoir via an oxygen line. Oxygen line  126  may facilitate transfer of oxygen from the one or more sieve beds to the liquid oxygen reservoir, in some embodiments. The oxygen extracted at the one or more sieve beds is liquefied between the one or more sieve beds and the liquid oxygen reservoir. In accordance with some embodiments, heat exchanger  128  liquefies oxygen extracted at the one or more sieve beds. 
     At operation  306 , a whole or partial blockage within the oxygen line is detected based on a liquid oxygen production rate or flow rate of gaseous oxygen, wherein the whole or partial blockage is caused by frozen water. According to various embodiments, controller  104  performs operation  306  in conjunction with temperature sensor  136  and/or flow sensor  138 . 
     At operation  308 , a valve is triggered to route air from the compressor to an air line in thermal contact with the oxygen line rather than to the one or more sieve beds responsive to detection of a whole or partial blockage within the oxygen line. In accordance with some embodiments, valve  112  is triggered by controller  104  to route air from gas compressor  110  to defroster air line  124  rather than PSA sieve beds  114 . 
     At operation  310 , the oxygen line is defrosted to melt frozen water within the oxygen line using heat provided by the air line. In some embodiments, defrosting the oxygen line includes carrying air from gas compressor  110  via defroster air line  124  such that heat is transferred from defroster air line  124  to oxygen line  126  due to thermal contact between defroster air line  124  and oxygen line  126 . 
     In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. 
     Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.