Miniature water quality monitoring and early warning station based on PLC control

Abstract

The utility model provides a kind of miniature water quality monitoring early warning station based on PLC control, including installation cabinet front end face is provided with operation front panel, installation cabinet lower part is provided with cabinet base, electrical control box is installed on the upper portion of installation cabinet inner wall side end face, operation monitoring touch screen is set on the inner wall of installation cabinet opposite electrical control box, the box body of electrical control box is sequentially installed circuit breaker, 220V wiring terminal row, switching power supply, internet module, PLC, intermediate relay and 24V wiring terminal row by electrical copper guide rail;The lower portion of the inner cavity of installation cabinet is provided with monitoring early warning station, the water inlet of water pump inlet end on the monitoring early warning station is connected by PVC pipeline, water inlet connects steel wire hose to water source, water pump outlet is connected by PVC pipeline Three-way valve, Three-way valve one end is connected to backwash valve group, backwash valve group connects variable-diameter thin hose to the rear of the sensor mounting point on the flow guide groove into flow guide groove.

Description

Technical Field

[0001] This utility model belongs to the field of water quality monitoring, and specifically relates to a micro water quality monitoring and early warning station based on PLC control. Background Technology

[0002] Currently, ensuring water quality safety at key points such as water plant inlets, diversion channels, rivers, and sewage discharge outlets urgently requires real-time, accurate, and stable automated monitoring methods. However, the raw water quality in these areas is often complex and poor, rich in high concentrations of suspended solids and pollutants such as silt, algae, oil, and biofilms, posing a severe challenge to the long-term reliable operation of monitoring equipment. Traditional solutions have significant limitations: manual monitoring requires the construction of fixed laboratories, incurring high costs in civil engineering, specialized instruments, and manpower, and suffers from low monitoring frequency and delayed response, making it difficult to meet the real-time early warning needs of dispersed deployments and sudden pollution events; while automatic monitoring stations based on multi-parameter integrated sensors (such as diversion channel water intake or integrated cabinets) have lower initial investment and are easy to deploy, their core waterways (diversion channels, pipelines) are prone to blockage due to impurities during long-term operation in harsh water quality environments, and sensor probes may experience sluggish response, decreased sensitivity, zero-point drift, or even failure due to continuous contaminant adhesion (forming a coating layer or reaction layer), resulting in severely distorted monitoring data and a sharp decline in accuracy over time.

[0003] Therefore, persistent contamination, blockage, and adhesion of equipment and its key components (especially water channels and sensors) have become a core technological bottleneck restricting the accuracy, long-term stability, and maintenance-free operation of water quality monitoring in harsh raw water areas. Existing technological solutions cannot effectively balance cost, accuracy, and long-term reliability under harsh environments, making it difficult to support refined management and timely early warning of water quality safety. Against this backdrop, developing a miniaturized monitoring and early warning station that integrates intelligent anti-contamination technologies (such as efficient self-cleaning, anti-adhesion design, and contamination-resistant sensors) with industrial-grade automated control (based on high-reliability PLCs) to achieve long-term maintenance-free operation under harsh water quality conditions, high-precision data output, real-time automatic early warning, and flexible, low-construction deployment has become an urgent technological need to address industry pain points and enhance water resource security capabilities. This innovative direction aims to overcome the challenges of inaccurate and unstable measurements, providing crucial support for building a smart water and environmental monitoring network.

[0004] The following solutions exist for water quality monitoring in environments such as water plant inlets, diversion channels, rivers, and sewage discharge channels: 1. Manual monitoring: A water quality testing laboratory is built at the testing point. This method requires civil construction, specialized testing instruments and reagents, and dedicated personnel to test the water quality. When dealing with long distances and scattered locations, the investment is too large, and the manpower and resources are too high, making it difficult to meet the water quality monitoring requirements in a timely manner. 2. Automatic testing: Multi-parameter water quality monitoring stations are set up at the testing points (with water intake and testing via diversion channels or integrated water quality testing cabinets). This solution has a small investment, is easy to install, and reduces manpower. However, if the raw water quality is poor, impurities and pollutants will accumulate in the diversion channels and sensors of the multi-parameter water quality monitoring station after a long period of use, which will affect water flow and the accuracy of water quality measurement. In practical applications, inaccurate data will appear after a period of use.

[0005] The main problems faced in water quality monitoring in areas with poor raw water quality are pollution of equipment by raw water, blockage of pipelines, and attachment of impurities to sensors. These factors seriously affect the accuracy of water quality monitoring and pose a significant challenge to the long-term operation of monitoring equipment. Therefore, it is particularly important to develop a water quality monitoring device that can operate in a long-term, stable, accurate, and automated manner. Utility Model Content

[0006] This invention proposes a PLC-controlled miniature water quality monitoring and early warning station, providing a highly integrated and anti-interference miniature water quality monitoring and early warning station. Through a compact cabinet with layered layout, multi-level anti-blockage pipeline design, and intelligent protection mechanism, it solves the problems of easy clogging, low-temperature freezing, and difficult maintenance of outdoor water quality monitoring equipment in complex environments, and achieves long-term stable operation and remote monitoring.

[0007] The technical solution of this utility model is implemented as follows: A micro water quality monitoring and early warning station based on PLC control includes an operation front panel on the front side of the mounting cabinet, a cabinet base at the bottom of the mounting cabinet, an electrical control box mounted on the upper part of the inner wall side of the mounting cabinet, and an operation monitoring touch screen mounted on the inner wall of the mounting cabinet opposite the electrical control box. Inside the electrical control box, a circuit breaker, a 220V terminal block, a switching power supply, an IoT module, a PLC, an intermediate relay, and a 24V terminal block are sequentially mounted via electrical copper rails. A monitoring and early warning station is located in the lower part of the inner cavity of the mounting cabinet, and the water pump inlet of the monitoring and early warning station is connected to... A PVC pipe connects to the water inlet, which in turn connects to a steel wire hose leading to the water source. The water pump outlet connects to a three-way valve via a PVC pipe. One end of the three-way valve connects to a backwash valve assembly, which in turn connects to a reducing hose leading to the sensor mounting point on the guide channel and into the guide channel. The other end of the three-way valve connects to the bottom of three guide channels via PVC pipes. The bottom of the leftmost guide channel connects to a drain valve, which connects to the water outlet. A filter valve connects the drain valve to the guide channel. The top of the guide channels converges into a straight PVC pipe equipped with an air vent valve and a flow switch, leading downwards to the water outlet. Temperature and humidity sensors and a semiconductor heater are installed inside the cabinet near the piping.

[0008] Existing outdoor water quality monitoring equipment has significant drawbacks: weak resistance to pollution: traditional pipeline designs easily lead to impurities clogging sensors, requiring frequent manual cleaning, resulting in high maintenance costs and affecting data continuity; insufficient environmental adaptability: pipelines are prone to freezing and damaging sensors in low-temperature environments, and conventional heating solutions are energy-intensive and have inaccurate temperature control; poor cabinet sealing easily leads to electrical faults; redundant structure and complex maintenance: the monitoring unit and control system are separately arranged, occupying a large space; sensor disassembly and assembly require water and pump shutdown, affecting monitoring efficiency.

[0009] The core technical challenge lies in balancing anti-clogging and monitoring: ensuring sufficient water flow to contact the sensor while efficiently discharging contaminants. This solution overcomes the limitations of traditional unidirectional flow systems, which cannot simultaneously achieve monitoring and self-cleaning, by using a vertical counter-current design of the guide channel (where impurities settle at the bottom) combined with a variable-diameter hose in the backwash valve assembly for reverse spraying (targeted flushing of the sensor). Miniaturization and functional integration are also key: the water circuit, electrical control, and temperature control systems are integrated layered within a limited cabinet, and the exhaust and flow detection functions are integrated using the manifold at the top of the guide channel, reducing redundant piping. A new filter valve intercepts large particles of impurities, further simplifying maintenance. Low-temperature protection ensures accuracy: the semiconductor heater and temperature and humidity sensor work together to create a localized constant temperature environment, preventing sensor data drift caused by direct heating.

[0010] In a preferred embodiment, the guide channel is a vertically arranged PVC pipe with a drain outlet at the bottom connected to a drain valve and an exhaust outlet at the top that flows into an exhaust pipe; the sensor mounting point is located on the upper side wall of the guide channel.

[0011] In a preferred embodiment, the three-way valve is a manual / automatic integrated electric valve, and its electric actuator is electrically connected to the output terminal of the PLC in the electrical control box; the drain valve is a manual / automatic integrated electric valve, and its electric actuator is electrically connected to the output terminal of the PLC in the electrical control box.

[0012] In a preferred embodiment, the flow switch signal output terminal is connected to the PLC input terminal of the electrical control box, and the flow switch is used to detect the water flow status during water pump operation; the control terminal of the semiconductor heater is connected to the PLC input terminal of the electrical control box through an intermediate relay and is triggered by the temperature and humidity sensor signal.

[0013] In a preferred embodiment, the sensor is a threaded interface type digital water quality sensor, whose data output terminal is connected to a multi-parameter data acquisition terminal, which is connected to the PLC of the electrical control box through a communication module.

[0014] In a preferred embodiment, the IoT module is connected to the PLC in the electrical control box via an RS485 or Ethernet interface to upload water quality data to a remote platform.

[0015] After adopting the above technical solution, the beneficial effects of this utility model are as follows: Compared with the prior art, the main difference of this technical solution lies in the design of the pipeline-type flow guide channel and the addition of the backwashing function, which can flush the pipeline and sensor at regular intervals to keep the pipeline unobstructed and the sensor surface clean. These improvements and innovations enable this solution to operate stably for a long time when facing poor raw water quality, and it is simple to operate, transmits data remotely, is unattended, and is easy to maintain. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a front view of the mounting cabinet of this utility model;

[0018] Figure 2 This is a schematic diagram showing the installation cabinet of this utility model after it has been opened;

[0019] Figure 3 This is a schematic diagram of the monitoring and early warning station structure of this utility model;

[0020] Figure 4 This is a flowchart of the waterway operation of this utility model;

[0021] Figure 5 This is a flowchart illustrating the operation of this utility model.

[0022] In the diagram, 1-installation cabinet; 2-operation front panel; 3-cabinet base; 4-electrical control box; 5-monitoring touch screen; 6-water inlet; 7-water pump; 8-air vent valve; 9-three-way valve; 10-backwash valve assembly; 11-sensor; 12-flow guide channel; 13-flow switch; 14-drain valve; 15-filter valve; 16-water outlet. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] Example:

[0025] like Figures 1-5 As shown, a micro water quality monitoring and early warning station based on PLC control includes a mounting cabinet 1 with an operation front panel 2 on its front side, a cabinet base 3 at the bottom of the mounting cabinet 1, an electrical control box 4 mounted on the upper part of the inner wall side of the mounting cabinet 1, and an operation monitoring touch screen 5 mounted on the inner wall of the mounting cabinet 1 opposite the electrical control box 4. Inside the electrical control box 4, a circuit breaker, a 220V terminal block, a switching power supply, an IoT module, a PLC, an intermediate relay, and a 24V terminal block are sequentially mounted via electrical copper rails. A monitoring and early warning station is located in the lower part of the inner cavity of the mounting cabinet 1. The water pump 7 on the monitoring and early warning station has its inlet connected to an inlet 6 via a PVC pipe, and the inlet 6 is connected to a steel... A flexible hose leads to the water source. The outlet of the water pump 7 is connected to a three-way valve 9 via a PVC pipe. One end of the three-way valve 9 is connected to the backwash valve assembly 10. The backwash valve assembly 10 is connected to a variable diameter flexible hose that enters the guide channel 12 behind the sensor 11 installation point. The other end of the three-way valve 9 is connected to the bottom of three guide channels 12 via PVC pipes. The bottom of the leftmost guide channel 12 is connected to a drain valve 14. The drain valve 14 is connected to the outlet 16. A filter valve 15 is connected between the drain valve 14 and the guide channel 12. The top of the guide channel 12 converges into a straight PVC pipe and is equipped with an air vent valve 8 and a flow switch 13. The pipe leads downward to the outlet 16. The temperature and humidity sensor and the semiconductor heater are installed inside the cabinet near the pipes.

[0026] The specific structure and component relationships in this application are as follows: The overall structure is a cabinet with a height of 1450mm, a width of 600mm, and a depth of 600mm. The main internal components are a water pipeline monitoring section, a PLC control section, and an auxiliary temperature control section. The pipeline section is installed in the lower part of the cabinet. The water pump 7's inlet is connected to the water inlet 6 via a PVC pipe. The water inlet 6 is connected to a steel wire hose leading to the water source. The water pump 7's outlet is connected to a three-way valve 9 via a PVC pipe. One end of the three-way valve 9 is connected to the backwash valve assembly 10. The backwash valve assembly 10 is connected to a reducing hose leading to the sensor 11 mounting point on the guide channel 12, and then into the guide channel 12. The three-way valve... 9. The other end is connected to the bottom of the three sets of guide channels 12 through PVC pipes. The bottom of the leftmost guide channel 12 is connected to the drain valve 14, and the drain valve 14 is connected to the outlet 16. The top of the three sets of guide channels 12 converges into a PVC straight pipe and is equipped with an exhaust valve 8 and a flow switch 11. It leads downward to the outlet 16. The temperature and humidity control and semiconductor heater are installed inside the cabinet near the pipeline. The upper part of the cabinet is equipped with an electrical control box 4. The front door panel of the box has an opening for a touch screen 5. The circuit breaker, 220V terminal block, switching power supply, IoT module, PLC, intermediate relay and 24V terminal block are installed in sequence inside the box through electrical copper rails.

[0027] The piping is made of PVC, which is pressure-resistant, corrosion-resistant, and has a good water seal, ensuring a long service life and suitability for various water quality environments. The guide channel adopts a PVC pipe design, with water flowing from bottom to top during operation. Impurities and contaminants in the water can be concentrated at the lower end of the guide channel and discharged during backwashing. The sensor is installed on the guide channel and secured with threads, making installation and disassembly convenient. Backwashing is based on PLC control, which controls the status of the three-way valve and drain valve to achieve backwashing. During backwashing, the water flow through the variable diameter hose of the backwash valve group generates a pressurized water column. The pressurized water column flows to the sensor inside the upper end of the guide channel, flushing the sensor surface and the inside of the pipe. The water flow is from top to bottom, flushing contaminants on the sensor surface and inside the guide channel with the water flow through the drain valve. Backwashing achieves self-cleaning, effectively ensuring long-term stable operation of the equipment in environments with poor water quality. Protective features are included during operation. The system features include: an air vent valve to promptly release excess air from the pipeline during water flow, reducing pipeline vibration and ensuring even water flow; a flow switch to detect water flow during operation and promptly stop operation if no water flow is detected for an extended period, ensuring pump safety; a semiconductor heater to activate when the temperature is below 5°C to prevent pipeline freezing; and manual / automatic electric valves for both three-way and drain valves, allowing for manual operation during commissioning or troubleshooting for easy maintenance. Water quality testing is achieved using digital sensors with various models available. These sensors connect to a multi-parameter data terminal, which automatically identifies the sensor model and allows for setting sensor parameters, calibration, and viewing historical data and curves. The collected data is integrated with a backend data platform using IoT technology, supporting multiple protocol forwarding protocols.

[0028] In manual mode, the system is operated via a touchscreen. The system controls the start and stop of the water pump and drain valve on the touchscreen. The three-way valve and drain valve in the pipeline can be manually opened and closed on the valve body. Manual mode is mainly used for initial operation, debugging, maintenance, and repair.

[0029] In automatic mode, the operation is controlled by a PLC and consists of three stages: backwashing, water sample replacement, and water quality testing. The operation is carried out in a timed cycle, and the time for each stage can be set and adjusted.

[0030] Backwashing: During backwashing, water flows through the variable diameter hose of the backwash valve assembly to generate a pressurized water column. The pressurized water column flows to the sensor inside the upper end of the guide channel, rinsing the sensor surface and the inside of the pipeline. The water flows from top to bottom, and the contaminants on the sensor surface and in the guide channel are discharged through the drain valve with the water flow. This process takes about 5 minutes. After it is completed, the lower part of the operation begins.

[0031] Water sample replacement: The water pump is started, the three-way valve is switched to the direction of the guide channel, the drain valve is closed, and the raw water is drawn in from the inlet by the water pump, flows through the three-way valve to the guide channel, flows from bottom to top in the guide channel, and finally is discharged through the flow switch and the drain outlet. This step is mainly to replace the water sample, so that the water sample tends to be stable and the actual water quality of the water sample is obtained. This step takes 3-5 minutes.

[0032] Water quality testing: After water sample replacement, the water sample and water flow tend to stabilize. At this time, water quality testing begins. The sensor data is analyzed and processed by the multi-parameter data terminal and then uploaded. This step takes about 5 minutes. After completion, wait for the waiting time and then repeat the above steps.

[0033] The miniature water quality monitoring and early warning station is installed on a solid, flat surface near the riverbed, with a concrete base as its foundation. Sensors are installed at the diversion channel, and the station is connected to a 220V AC power supply. The inlet and outlet are connected to flexible steel hoses, with PVC pipes laid over them to protect them. The outlet pipe is reserved at a convenient location along the riverbank. The inlet pipe extends into the river surface along with the PVC outer pipe. Sufficient length of the flexible steel hose is provided in the water (to accommodate the minimum and maximum water level difference). The flexible steel hose connects to a float, and raw water is pumped in after passing through the float to filter solid impurities. The distance from the pipeline to the monitoring point in the river should not exceed 20m, and the vertical distance from the water surface to the monitoring station should not exceed 4m.

[0034] The guide channel 12 is a vertically arranged PVC pipe. Its bottom end has a drain outlet connected to a drain valve 14, and its top end has an exhaust outlet that merges into an exhaust pipe. The sensor 11 is installed on the upper side wall of the guide channel 12. The guide channel 12 uses a vertically arranged PVC pipe with a drain outlet at its bottom, directly connected to the inlet of the drain valve 14. An exhaust outlet is located at the top of the guide channel 12, merging with exhaust outlets from other guide channels via a PVC pipe, and connecting to the main exhaust pipe. The sensor 11 is screwed into a pre-reserved threaded interface on the upper side wall of the guide channel 12, achieving a sealed fixation and water flow connection. Function: The vertical pipe allows water to flow from bottom to top, causing impurities to settle near the drain outlet at the bottom of the channel; the sensor is installed in a stable water flow area, and the threaded interface ensures that the pipeline is not interrupted during installation and disassembly.

[0035] The three-way valve 9 is a manual / automatic integrated electric valve, and its electric actuator is electrically connected to the PLC output terminal in the electrical control box 4. The drain valve 14 is also a manual / automatic integrated electric valve, and its electric actuator is electrically connected to the PLC output terminal in the electrical control box 4. Electrical connection path: The electric actuator of the three-way valve 9 is connected to the PLC output terminal in the electrical control box 4 via a cable; the electric actuator of the drain valve 14 is connected to another PLC output terminal in the electrical control box 4 via a separate cable; both valves retain a manual operation knob (manual / automatic integration feature) for direct mechanical operation of the valve core during power outages or debugging. Function: The PLC output signal drives the valve motor to achieve automatic water circuit switching; the manual knob serves as hardware redundancy.

[0036] The signal output terminal of the flow switch 13 is connected to the PLC input terminal of the electrical control box 4. The flow switch 13 is used to detect the water flow status during water pump operation. The control terminal of the semiconductor heater is connected to the PLC input terminal of the electrical control box 4 through an intermediate relay and is triggered by the temperature and humidity sensor signal. Electrical signal link: The signal output line of the flow switch 13 is connected to the input terminal (such as DI module) of the PLC in the electrical control box 4; the signal output line of the temperature and humidity sensor is connected to the input terminal of the PLC in the electrical control box 4; the power supply line of the semiconductor heater is controlled by the intermediate relay coil, which is powered by the PLC output terminal, and the relay contacts are connected in series with the heater main circuit.

[0037] The sensor 11 is a threaded interface type digital water quality sensor. Its data output terminal is connected to a multi-parameter data acquisition terminal, which is connected to the PLC of the electrical control box 4 via a communication module. The data line of the sensor 11 (such as an RS485 interface) is connected to the input port of the multi-parameter data acquisition terminal; the communication interface of the multi-parameter data acquisition terminal (such as Ethernet) is connected to the communication module (such as CP341) of the PLC in the electrical control box 4 via a cable.

[0038] The IoT module connects to the PLC inside the electrical control box 4 via an RS485 or Ethernet interface to upload water quality data to a remote platform. The IoT module (such as a 4G DTU) is directly plugged into the PLC's RS485 communication terminal or connected to the PLC's Ethernet port via a network cable; the IoT module's antenna interface is connected to an external communication antenna for wireless data upload.

[0039] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A micro water quality monitoring and early warning station based on PLC control, characterized in that, The installation includes an operation front panel (2) on the front side of the mounting cabinet (1), a cabinet base (3) at the bottom of the mounting cabinet (1), an electrical control box (4) on the upper side of the inner wall of the mounting cabinet (1), and an operation monitoring touch screen (5) on the inner wall of the mounting cabinet (1) opposite the electrical control box (4). The electrical control box (4) contains a circuit breaker, a 220V terminal block, a switching power supply, an IoT module, a PLC, an intermediate relay, and a 24V terminal block, all installed sequentially via electrical copper rails. A monitoring and early warning station is located at the lower part of the inner cavity of the mounting cabinet (1). The water pump (7) on the monitoring and early warning station has its inlet connected to a water inlet (6) via a PVC pipe. The water inlet (6) is connected to a steel wire hose leading to the water source. The water pump (7) has its outlet connected to a... A PVC pipe is connected to a three-way valve (9). One end of the three-way valve (9) is connected to a backwash valve assembly (10). The backwash valve assembly (10) is connected to a variable diameter flexible hose to the back of the sensor (11) installation point on the guide trough (12) and enters the guide trough (12). The other end of the three-way valve (9) is connected to the bottom of three guide troughs (12) through a PVC pipe. The bottom of the leftmost guide trough (12) is connected to a drain valve (14). The drain valve (14) is connected to the outlet (16). A filter valve (15) is connected between the drain valve (14) and the guide trough (12). The top of the guide trough (12) is joined into a PVC straight pipe and equipped with an exhaust valve (8) and a flow switch (13). The pipe leads downward to the outlet (16). The temperature and humidity control and semiconductor heater are installed inside the cabinet near the pipe.

2. The micro water quality monitoring and early warning station based on PLC control as described in claim 1, characterized in that: The guide channel (12) is a vertically arranged PVC pipe. The bottom end of the guide channel (12) is provided with a drain outlet connected to a drain valve (14), and the top end is provided with an exhaust outlet that flows into an exhaust pipe. The sensor (11) is installed at the upper side wall of the guide channel (12).

3. A micro water quality monitoring and early warning station based on PLC control as described in claim 1, characterized in that: The three-way valve (9) is a manual-automatic electric valve, and its electric actuator is electrically connected to the output terminal of the PLC in the electrical control box (4); the drain valve (14) is a manual-automatic electric valve, and its electric actuator is electrically connected to the output terminal of the PLC in the electrical control box (4).

4. A micro water quality monitoring and early warning station based on PLC control as described in claim 1, characterized in that: The signal output terminal of the flow switch (13) is connected to the PLC input terminal of the electrical control box (4). The flow switch (13) is used to detect the water flow status during the operation of the water pump. The control terminal of the semiconductor heater is connected to the PLC input terminal of the electrical control box (4) through an intermediate relay and is triggered by the temperature and humidity sensor signal.

5. A micro water quality monitoring and early warning station based on PLC control as described in claim 1, characterized in that: The sensor (11) is a threaded interface type digital water quality sensor, and its data output end is connected to a multi-parameter data acquisition end, which is connected to the PLC of the electrical control box (4) through a communication module.

6. A micro water quality monitoring and early warning station based on PLC control as described in claim 1, characterized in that: The IoT module is connected to the PLC in the electrical control box (4) via an RS485 or Ethernet interface to upload water quality data to a remote platform.

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