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\title{Economical Real-Time Monitoring of Power Consumption} 
\author{Colin Copeland}
\date{\today}

\begin{document}
  \maketitle

  \tableofcontents

  \section{Introduction}
  Energy is a crucial national and international concern. It's tied closely to
  environmental problems, much of it is imported, and unequal global
  consumption raises questions of international resource equity and
  sustainability \cite{smoot}. The total United States energy consumption in
  1992 was 82.4 quads of energy, more than any year in the past and accounts
  for one-fourth of global energy use, despite having less than 5\% of the
  total world population. Coal, the most significant energy source for
  electricity, has a vast reserve base exceeding 425 billion metric tons across
  32 states, far exceeding both natural gas and crude oil, whose reserves are
  fairly limited \cite{tillman}.  One estimate \cite{ashworth} on natural gas
  world reserves believes about 5,100 trillion cubic feet (TCF) of natural gas
  remains, while the United States currently consumes 22 TCF annually. Further,
  fossil fuel usage is tied very closely to environmental concerns. The
  combustion of coal produces nitrogen and sulfur oxides that are the key
  causes of acid rain and nitrogen oxide can lead to an increased production of
  ozone in the troposphere and stratospheric ozone depletion \cite{smoot}. The
  burning of natural gas, like other fossil fuels, produces carbon dioxide, but
  almost no other waste other than water vapor \cite{tillman}. Regrettably, the
  most serious environmental effects of actions made today will occur in the
  future. Long lasting changes in consumer behavior are needed.

  \begin{figure}
    \centering
    \includegraphics{graphics/02residential_energy_sources.eps}
    \caption{Residential Energy Sources \protect \cite{komor}}
    \label{residentialEnergyNeeds}
  \end{figure}

  As shown in Appendix A, the industrial sector leads in energy
  consumption, consuming almost twice as much as the residential and commercial
  sectors combined. Public utility companies can spend time with large
  industrial consumers to help reduce energy consumption. However, there are
  many, many consumers, so this method would not be cost effective for utility
  companies to spend time with every single small consumer. Therefore, some
  consumers must be approached in a different way.

  In an interview with Gregg Duke of Richmond Power and Light (RPL), I inquired
  about their metering equipment and their communication with consumers about
  reducing energy.  Richmond Power and Light offers on sight monitoring
  services to residential, commercial, and industrial consumers. Using Data
  Acquisition Units (DAQ), they have the ability to monitor every circuit to
  isolate energy consumption, which can then be compared to the over all
  bills. RPL believes consumers are very interested in their usage, as the DAQ
  units constantly remain in the field.

  \begin{quote}
    We tend to think the residential customers don't have a lot of
    sophistication that you generally associate with an industrial customer,
    but there's still a lot of sophistication in a residential audit. You go to
    a residence and there's a lot more education to it then there is data
    analysis.
  \end{quote}

  Generally, residences contact RPL about saving money. For example, a common
  concern is with heating bills. The first step taken is to educate the
  customer ---inform them about programmable thermostats, more efficient
  appliances, or encourage them to look into alternative types of heating
  systems, like geothermal heating and they investigate other large energy
  users, like dehumidifiers and air conditioners. Further, in relation to
  utilities spending time with larger customers, they've setup test systems to
  allow industrial consumers to closely monitor consumption. For example, a
  wireless web server continuously monitors Hill's Pet Nutrition Inc. around the
  clock, allowing workers to log on track their consumption at any
  time. Monitoring usage statistics and collecting continuous data over time
  allows the information to be quantified for the consumer, ``a picture is
  worth a thousand words, and that's no joke here... If you educate them, they
  will change.''

  Figure \ref{residentialEnergyNeeds} shows that natural gas and electricity
  are significant energy sources for residential energy consumption. Monitoring
  gas use would require severing gas lines, which is possible, but not the
  easiest method. Electricity is an easier resource to monitor, because
  monitoring equipment can be installed without interrupting the service. How
  can we help people change their behavior and conserve?

  \section{Feedback, Behavior, and The Consumer}
  Energy use is generally invisible to the consumer \cite{darby1}. Domestic
  energy use, being limited to monthly utility bills, is directed towards the
  cost of each utility, and leads consumers to think solely in terms of dollars
  per month. People may hold vague ideas about their energy consumption, but it
  usually doesn't concern their day-to-day behavior and activity. Although
  single everyday actions use small amounts of energy on a national scale
  (aggregated across millions of people and billions of occasions) they must be
  taken into consideration \cite{stern}.

  For that reason, there must be a focus on behavior. Consumer behavior is
  influenced by feedback and Darby outlines various types of feedback,
  including: direct, indirect, and inadvertent \cite{darby1}.

  Direct feedback is available on demand; the consumer learns by looking or
  paying. Self-meter-reading, direct display, and interactive feedback via a PC
  are all examples of direct feedback. All involve having direct access at any
  time to information. This can be as simple as walking outside to read utility
  meters. Further, a computer can be used to present feedback information,
  possibly displaying consumption statistics over time or allowing the
  homeowner to interact with the data (view specific time periods, change the
  rate feedback, generate graphs, etc).

  Indirect feedback is learning by reading and reflecting. Rather than seeing
  how certain activities directly effect energy consumption with frequent
  feedback, the feedback is presented indirectly, in that the data is processed
  by the utility and sent out to customers on a larger time scale. Utility
  bills are examples of indirect feedback; they can be very detailed with
  historical information, etc, but are less frequent. Therefore the consumer
  reads and reflects on what they did, rather than seeing their actions
  directly effect the feedback, i.e. looking at a meter and seeing how a space
  heater consumes electricity.

  Finally, inadvertent feedback is learning by association. For example: small
  scale micro-generation. In contrast to energy consumption, micro-generation
  allow homes to generate energy through the use of photovoltaic (PV) arrays,
  wind turbines, etc. Generation on a small scale forces consumers to watch
  their energy habits closely. Weather can directly effect energy production
  ---cloud cover and calm days greatly decrease energy production. Home owners
  learn to pay attention to weather changes, changing their behavior
  accordingly. This form of inadvertent feedback leads consumers to not only
  monitor their battery banks on a day-to-day basis, but to be aware of the
  weather as well. They're the fully informed and aware consumers.

  \begin{figure}
    \centering
    \includegraphics{graphics/feedback.eps}
    \caption{Feedback and Behavior}
    \label{feedbackbehavior}
  \end{figure}
  
  Beyond the various forms of feedback, an integral aspect lies in with how it
  effects the consumer. van Houwelingen and van Raaij outline the functions of
  feedback. Information through feedback is used as a basis for
  improvement. For example, consumers may not be aware of changes they can make
  to conserve energy.  However, they can learn to understand the results of
  their actions through different types of feedback and reduce their
  uncertainty. van Houwelngen and van Raaij believe this influences habit
  formation. Subsequently, as habits are being set and reinforced, people are
  behaving in an ``energy conscious way'' and this behavior causes people to
  adapt new attitudes on energy conservation \cite{jeannet}. Figure
  \ref{feedbackbehavior} shows Darby's various forms of feedback and illustrates
  van Houwelngen and van Raaig's functions of behavior.

  Further, the method by which feedback in conveyed is very important
  ---display, frequency, and presentation improve it's quality. Energy use
  feedback with better message presentation can lead to energy savings of 10\%
  to 20\% through direct energy-saving actions \cite{stern}. Therefore,
  combining data frequency with better presentation can lead to substantial
  savings. ``Feedback adds no information beyond what is already on people's
  utility meters, but it provides the information soon after any behavior
  change, and in a vivid and easily understandable manner'' \cite{stern}.

  While the quantity of information provided to the consumers is important, the
  main goal is a presentation to capture their attention. In order to sustain
  consumer attention, the information should be persuasive enough to penetrate
  into their day-to-day activities.

  \begin{quote}
    Behaviorally, investment is a one-time action, whereas management and
    curtailment require changing behavior patterns and continuously maintaining
    the changed behavior. We would thus expect that management and curtailment
    would require more frequent feedback to make visible the energy effects of
    changed behavior. \cite{kempton}
  \end{quote}

  Purchasing energy efficient appliances (e.g., hot water heater, refrigerator,
  etc), thermostats that automatically reduce heating/cooling use at night, low
  flow water utilities, etc, are all one time investments that can
  significantly reduce energy use. However, there is very little behavioral
  change in consumers. According to \cite{darby1} and \cite{jeannet},
  curtailment is achieved by consumers learning through feedback and developing
  habits to reduce consumption,

  The below studies analyze various forms of feedback, including public
  feedback, feedback frequency, and goal setting with feedback.

  \subsection{Public Posted Feedback}

  Displaying information for public viewing can bring about a reduction in
  certain behaviors. A study \cite{houten} performed in Dartmouth, Nova Scotia,
  compared the effectiveness of publicly posted feedback with increased police
  surveillance on highways. The test focused on a four-lane divided highway
  where the speed limit decreased from 80 km/h to 50 km/h entering an urban
  area. A large sign, placed adjacent to the speed limit sign, displayed the
  percentage of drivers traveling under the speed limit the previous week
  (``Drivers Not Speeding Last Week'') and the highest percentage achieved to
  (``Best Record''). 
  
  The study showed that public posting achieved greater percentage reductions
  relative to the baseline averages than the police radar surveillance and
  ticketing, concluding that public posting was at least 10 times more
  efficient in controlling speeding \cite{houten}. The researchers believe that
  ``strict enforcement is not effective in reducing speeding behavior''
  \cite{houten}, and suggests the driver slows down only when the police
  vehicle is visible to him.
  
  This form of indirect feedback is unique, in that it's approach is a public
  posting. The posting displays speeding information relating to drivers as a
  group, while the feedback is reflected upon individually by each
  driver. Drivers reflect on not only their personal speeding behavior, but see
  where they stand in relation to the average driver. Therefore, the drivers
  ideology plays a significant role in their behavior (i.e. considering their
  effect on the group as a whole and slowing down or reflecting on the posting
  solely as an individual and feeling speeding is OK because the average is
  low).

  In conclusion, public posted feedback brought about a significant reduction
  in the number of speeding drivers. The average was decreased, even though not
  everybody probably participated in the reduction. 

  \subsection{Simple Meter Reading}
  The study was performed on 40 homeowners in identical three-bedroom town
  houses in New Jersey. During the summer months, after recording baseline
  values, homeowners were told they were in an energy study and were informed
  of energy saving techniques (focused primarily on air conditioning, which
  consisted of 70\% of the electricity used by the homes \cite{seligman}). The
  households were then randomly assigned to a control or feedback group.

  For the feedback group, a research assistant read the electric meters on a daily
  basis to calculate the consumption. They also maintained a predicted performance
  value, which was calculated using the last 24-hour consumption value and hourly
  temperature readings. Therefore, using a regression equation, the researchers
  could predict daily electric consumption from average temperature readings
  \cite{seligman}. Every day at 5:00 PM, each households consumption value, along
  with their prediction, was inserted into a 5 x 3 inch plastic number display that
  was set up in the kitchen window. Homeowners could then see how well they
  performed the previous day in comparison to their predicted performance. The
  predicted value is, in effect, the target or goal each homeowner can strive to
  achieve.

  In the end, the feedback group consumed 10.5\% less electricity than the
  control group --suggesting direct feedback significantly assisted in
  consumption reduction. In comparison to the previous study, feedback focused
  on the homeowners individually, rather than combining and displaying the
  information to their neighbors. The plastic number display could very well
  have been turned around to face their neighbors, allowing the surrounding
  households to see each homeowners consumption reduction as well. The results
  might have been much different. A combination of both methods could possible
  have achieved the greatest reduction.

  On a separate note, the researchers opted not to use an automatic monitoring
  system:

  \begin{quote}
    A totally automated system to give feedback is by no means beyond the range
    of engineering technology: Electrical components are available from which
    such a system could be constructed, but we did not attempt to build it for
    the present study. Cost and time-consuming problems are involved in
    producing several devices that would be reliable and cheap.
    \cite{seligman}
  \end{quote}

  The participating households agreed to allow a researcher to enter their yard
  and read the electric meter. Would more frequent or detailed feedback, which
  would have been impossible with the method they used, have changed the
  average consumption reduction?

  While direct feedback significantly effected consumption, many questions
  still remained unanswered. For example, no post-experimental data was
  collected. How long will the effects of feedback persist after the study?
  Maybe the information presented in feedback could have changed. Would
  displaying the feedback in dollars and cents been more effective?
  
  \subsection{Setting Goals with Natural Gas Consumption}
  A natural gas conservation study \cite{jeannet} focused on a large number of
  identical rental homes in Nieuwegein, Netherlands. Most Dutch homes are
  heated with natural gas. A subset of the total of the 325 participating
  families agreed to strive for a savings of 10\%, while the houses that did
  not agree to the conservation goal were assigned to a separate control
  group. Fifty select households received electronic devices to monitor natural
  gas use, called ``Indicators'', which displayed the daily amount of natural
  gas in comparison with the conservation goal. The rest of the testing group
  was divided into two groups: one received monthly external feedback about
  their gas use and the other monitored their own gas use by looking at their
  utility meters.

  The study hypothesized the following:
  \begin{enumerate}
  \item Goal-setting and the use of the Indicator (plus information about
    energy conservation) will reduce the use of natural gas for home heating.
  \item The reduction of gas use in the Indicator condition will be larger than
    in the monthly external feedback and self-monitoring conditions.
  \item The reduction of gas use in the experimental conditions will be larger
    than in the control conditions (if there is a reduction in the control
    conditions at all).
  \item The reduction of energy use use in the Indicator condition (and in the
    other experimental conditions) will last after the experimental period of
    one year; i.e., there will be a significant difference between the
    experimental and the control groups in long-term effects.
  \end{enumerate}

  \begin{figure} 
    \centering \includegraphics{graphics/05natural_gas.eps}
    \caption{Feedback comparisons for participating groups in natural gas study
      \protect \cite{jeannet}} 
    \label{jeannet} 
  \end{figure}

  Experimental groups are shown in relation to their presentation frequency and
  quality in Figure \ref{jeannet}. The self monitoring group with limited
  presentation quality (reading consumed therms on standard meters outside of
  the household) had the option of checking their meters as frequently as
  desired (direct feedback), but ended up tailing the other two groups with an
  average reduction of 5.1\%. The informed group, with feedback on a monthly
  basis (indirect feedback, less frequent), received detailed reports of their
  consumption patterns in the mail and achieved an average reduction of 7.7\%.
  Finally, the greatest average reduction of 12\% was achieved by the Indicator
  group, who had feedback presented on digital displays in their living rooms
  (direct feedback).

  To test the fourth hypothesis, all testing conditions were removed from
  participating households and the energy used during the year following the
  experiment was recorded for each group. The results show that energy use in
  the groups (including the Indicator group) during the experimental period did
  not hold during the post-experimental period. This suggests that the feedback
  had an effect only during the period it was given and that no long term habit
  formation or internalization occurred.

  In conclusion, energy monitoring feedback presented to participants with a
  goal-setting ideology has a positive effect on energy
  conservation. Participants reported a growing awareness of their energy use
  and over half said they would like to have the Indicator installed
  permanently \cite{jeannet}. ``The Indicator has a positive impact on consumer
  knowledge of household energy use and helps residents reduce their gas use''
  \cite{jeannet}.  However, the post-experimental period implies the effects of
  energy monitoring feedback only lasts when present and residents may require
  a reminder in their home in order to save energy.

  \section{Proposal}

  Changing energy use behavior has a promising potential for energy
  conservation. Feedback plays a very important role in increasing consumer
  awareness. Timely feedback is helpful in guiding people to effective
  conservation behavior. Feedback presentation quality is important. The more
  unequivocally the feedback gives information, the more effect it has on the
  consumer. Feedback perspective is important to consumer ideology. Obviously,
  ones principals can greatly effect their commitment to conservation.
  Incorporating feedback inputs to encompass more than a single person and
  presenting a combined view to everyone involved, allows one to see not only
  how they're performing historically, but also to compare their efforts to
  that of their neighbors.

  Instrumenting feedback can be a costly process, but it proves to be more cost
  effective than other alternatives. Houten compared the cost effectiveness of
  police surveillance and the public posting procedure \cite{houten}. On the
  other hand, Seligman and Darley used man-hours instead of an automated system
  to implement their feedback presentation, stating ``cost and time-consuming
  problems are involved in producing several devices that would be reliable
  and cheap'' \cite{seligman}. van Houwelingen and van Raaij not only used
  man-hours to send detailed monthly reports to homeowners but also
  demonstrated the use of Indicators for gas consumption.

  Providing consumers with a permanent daily check can give greater insight
  into consumption for continuous services, like electricity, gas, water, etc.
  A cheap, cost-effective automated system can provide frequent feedback and
  implementing a well executed message presentation system to convey
  consumption information will help with energy conservation.

  \section{Earlham Energy Awareness Project} 

  The Earlham Energy Awareness Project (EEAP) is an incentive program to increase
  energy awareness of students living in campus housing. By promoting conservation
  efforts on campus, EEAP hopes to create a student body conscious of their
  consumption in hope of decreasing the environmental footprint of the college.
  EEAP collects the houses utility bills (electricity, gas, and water) every month.
  The quantity consumed for each utility is compared to a baseline consumption
  value (a three year rolling average for that month). If a house uses less energy
  than the baseline value, the difference is recorded. The three year rolling
  average is a target value for each house ---this goal is the same method used for
  the homeowners predicted value in the Simple Meter Reading study.

  The difference for each utility is displayed online on the EEAP website, so that
  students can monitor their conservation efforts. Detailed listings by utility and
  historical consumption information is available online as well. The website aims
  to achieve a high level of feedback quality and message presentation. Further,
  EEAP provides an interface for students to compare their conservation efforts to
  each other. This allows students to compete for a higher ranking in percentage
  reduction. Displaying this information publicly and allowing it to be easily
  compared, relates back to the public posting in the feedback and speeding study.

  To motivate student conservation, EEAP will reward the students by returning a
  percentage of their conservation efforts in money ---66\% of their savings. The
  remaining 33\% is returned to the college. This allows both the college and
  students to benefit from the project. At the end of each semester, the savings
  will be totaled and distributed to the house residents. Therefore, EEAP hopes to
  motivate students by rewarding them money for achieving a consumption level thats
  less than their target value (the three year rolling average).

  The method of feedback presented to the students relates closely to the feedback
  given to the ``Informed Group'' in the the natural gas conservation study.
  Feedback frequency is a key item missing in EEAP, which has the capability to
  display more information in an accessible way. What if the students had direct,
  frequent feedback, like the ``Indicator Group''? Students living in campus
  housing cannot purchase energy efficient hot water heaters, install proper
  insulation, etc. However, they can learn to reduce energy use with the utilities
  they have. As supported in the studies above, an automated power monitoring
  system can dramatically increase consumer awareness, more effectively than
  through indirect feedback. If students had access to live, frequent data, then
  they could focus on decreasing energy consumption. Hopefully, attitudes favorable
  to conservation will develop and help to sustain the motivation to the students.

  \section{EEAPnode Solution}

  \subsection{Develop Baseline System}

  First, I plan to develop a preliminary baseline system using a single board
  computer (SBC) connected to a power monitoring device called a WattNode.
  Continental Control Systems offers the WattNode, which is a true RMS AC
  watt-hour meter with TTL level pulse output proportional to kilowatt-hour
  consumed. Installation of the WattNode requires a direct connection to the
  circuit for voltage and current transformers (CT) to measure current.
  Continental Control Systems offers split core (opening) current transformers,
  which have a removable section, so that they can be installed without
  disconnecting the circuit being measured.

  \begin{figure} 
    \centering \includegraphics{graphics/07baseline_system.eps}
    \caption{Baseline System}
    \label{baselinesystem} 
  \end{figure}
  
  Technologic Systems offers compact single board computers (SBC). I chose to
  use the TS-5500, which is a standard x86-based PC compatible computer with an
  AMD Elan520 processor running at 133MHz. It boots a distribution of Linux off
  of a compact flash (CF) card for a simple development environment. The TS-5500
  is equipped with TTL level digital input/output (DIO) lines.

  Connecting the WattNode TTL level output to the TS-5500 (as shown in Figure
  \ref{baselinesystem}, I've written C-code to monitor the DIO ports on the
  board. My program uses kernel timers to poll the DIO ports at discrete
  intervals, checking to see if it registers a pulse. After making sure not to
  count the same pulse twice, the pulse count in incremented.  My code is
  attached in the appendix.

  \subsection{Build Sensor}

  \begin{figure} 
    \centering 
    \resizebox{4.5in}{!}{\includegraphics{graphics/insidewattnode.eps}}
    \caption{Replace functionality of WattNode with software running on the SBC}
    \label{inside} 
  \end{figure}

  The SBC and WattNode combination is expensive. Further, the SBC isn't being fully
  utilized. The WattNode uses hardware to monitor power consumption in real time
  and provides output in the form of pulses proportional the power consumed. It is
  basically converting an analog signal to a digital signal, which the TS-5500 can
  read on it's DIO ports. The same functionality could be performed in software on
  the TS-5500, as shown in Figure \ref{inside}. Alternating current (AC) in the
  U.S. is generated at 60 Hz, or 60 cycles per second. The TS-5500 is equipped with
  multiple 12-bit analog-to-digital (A/D) ports, capable of performing 20,000
  samples per second. Therefore, monitoring AC on the SBC is possible in software,
  allowing the SBC to be fully utilized and saving money by not using the WattNode.

  \subsection{Signal Conditioning and Calculating Power}

  \begin{figure} 
    \centering \includegraphics{graphics/11circuit.eps}
    \caption{Voltage divider and signal conditioning circuit}
    \label{circuit} 
  \end{figure}

  To measure current and voltage on the board, I need to do signal conditioning.
  The voltage measurement must take into account that the input voltage is
  120VAC. The TS-5500 has analog input ranges up to -10V to +10V, with each
  channel being over-voltage tolerant from -16V to +16V \cite{tsmanual}. In order
  to measure voltage and current safely, a circuit must be designed to condition
  signals enough to safely connect them to the board. I've built a
  voltage divider to step the voltage down to the TS-5500 levels, pictured in
  Figure \ref{circuit}. The current measurement can be assisted by the
  current transformer. The solid core current transformers offered by Continental
  Control Systems, produce 0.333 VAC output at rated current \cite{ctmanual},
  which means that a 30A rated current transformer will produce 0.3VAC when
  placed on a line with a load of 30 amps.

  In software, the SBC polls the A/D at discrete intervals to take instantaneous
  readings of current and voltage. In order to record the maximum number of
  readings per cycle, the SBC must dedicate all of it's time and processing power
  to my program. To ensure this, I wrote a module that runs in kernel space,
  allowing my program to disable interrupts before running in a tight loop to take
  its readings. This guarantees my program will remain active and not be swapped
  off so the SBC can handle other tasks. My module can then relinquish it's
  priority and allow the SBC to perform other tasks. Average power can then be
  calculated by dividing over the period (the number of recorded readings). This
  information is written into the proc filesystem, which is readable from user
  space.

  \subsection{Data Acquisition}

  In order to make the information presentable, it must be acquired from the SBC.
  Using kernel timers, a user program reads the proc file created by the power
  monitoring kernel module multiple times a second. It packages the information
  into a protocol data unit (PDU) and pushes the packet through a TCP socket. At
  the other end of the pipe, a server receives the packet and stores it in a
  postgres database.

  \subsection{Calibration} 

  \begin{figure} 
    \centering 
    \resizebox{6in}{!}{\includegraphics{graphics/10min.eps}}
    \caption{EEAPnode watt-hour calibration using WattsUp? Pro}
    \label{10min} 
  \end{figure}

  I calibrated against the WattsUp? Pro, a true RMS watt meter and electricity
  monitor. It includes an option to display the cumulative watt hours used since it
  was plugged in. Using a space heater and light board consisting of 5 light
  sockets, each powering a 100W incandescent light bulb, I ran a series of 10
  minute tests under various constant loads. I recorded the various watt-hours,
  plotted them against my values, and plotted linear regression line, as shown in
  Figure \ref{10min}. I used the linear equation to calibrate my readings.

  \subsection{Results}

  To test my results, I created a simple interface to display the total cumulative
  watt-hours recorded in the database. I ran an 80 minute test, recording both the
  EEAPnode and WattsUp? reported watt-hours. The results are shown in Figure
  \ref{10minresults}. The graph shows both meters inline early on, but begin to
  digress after about an hour. This is probably due to my calibration time being
  limited to a short 10 minute interval. Ideally, running a series of tests
  spanning longer periods of time would produce more accurate readings. I believe
  doing this would train the EEAPnode to be more accurate.

  \begin{figure} 
    \centering 
    \resizebox{6in}{!}{\includegraphics{graphics/10min-results.ps}}
    \caption{Results of EEAPnode against WattsUp?}
    \label{10minresults} 
  \end{figure}

  \pagebreak

  \bibliographystyle{mlaurl.bst}
  \bibliography{project.bib}

\end{document}
