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Hong Kong Polytechnic University - PolyU HK

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Hong Kong Polytechnic University

ENG224 Information Technology

Assignment+Lab Exercise for Part III

Instructions: - Answer all questions.

  • Use this file to prepare your solutions and submit it to WebCT before the due date.

  • Apply your commonsense knowledge whenever needed.

Assignment Questions

Q.1 a) Draw an Entity-Relationship diagram (ERD) containing the Patient, the Doctor, and the Visit entity types connected by 1-M relationships from Patient to Visit and Doctor to Visit. Choose appropriate names for the relationships. Define minimum cardinalities so that patients and doctors are mandatory for a visit, but visits are optional for patients and doctors.

For the Patient entity type, use the attributes Pat_ID (primary key), Pat_FName, Pat_LName, Pat_Address and Pat_HealthPlan. For the Doctor entity type, use the attributes Doc_ID (primary key), Doc_FName, Doc_LName, Doc_Specialty, Doc_Phone, and Doc_Hospital. For the Visit entity type, use the attributes Visit_No (primary key), Visit_Date, Visit_PayMethod (cash, check, or credit card), and Visit_Charge.

Apply your common sense knowledge to understand the attributes.

b) Extend your ERD in part (a) with the Nurse, the Item, and the VisitDetail entity types connected by 1-M relationships from Visit to VisitDetail, Nurse to VisitDetail, and Item to VisitDetail. VisitDetail is a weak entity with the 1-M relationship from Visit to VisitDetail an identifying relationship. Choose appropriate names for the relationship. Define minimum cardinalities so that a nurse is mandatory for a visit detail, an item is optional for a visit detail, and visit details are optional for nurses and items.

For the Item entity type, use the attributes Item_No (primary key), Item_Desc, Item_Price, and Item_type. For the Nurse entity type, use the attributes Nurse_ID (primary key), Nurse_FName, Nurse_LName, Nurse_Title, Nurse_Phone, Nurse_Specialty, and Nurse_PayGrade. For the VisitDetail entity type, use the attribute Detail_NO (part of the primary key) and Detail_Charge.

Q.2 Given the following Customer, OrderTbl, and Employee tables of a simplified Order Entry database.

  1. Write a CREATE TABLE statement for the Customer table. Apply your commonsense knowledge to choose data types for the attributes involved. Note that the CustBal contains numeric data and the currency symbols are not stored in the database. The CustFirstName and CustLastName columns are required (not null).



CustNo VARCHAR(8),

CustFirstName VARCHAR(5) NOT NULL,


CustCity CHAR(3),

CustState VARCHAR(2),

CustZip NUMBER(10,0),

CustBal NUMBER(6,2)


  1. Write a SQL statement to list the customer number, the name (first and last), and the balance of customers.

Download Information Technology - Assignment and Lab Exercise: Entity-Relationship diagram (ERD)
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SELECT CustNo, CustFirstName, CustLastName, , CustBal

FROM Customer

  1. Write a SQL statement to list the customer number, the name (first and last), the city, and the balance of customers who live in Seattle with a balance greater than $300 or who live in Denver with a balance greater than $150.

SELECT CustNo, CustFirstName, CustLastName, CustCity, CustBal

FROM Customer

WHERE (CustCity=’Seattle’ AND CustBal>300) OR (CustCity=’Denver’ AND CustBal>150)

  1. Write a SQL statement to list the employee number, name (first and last), and phone of employees who have taken orders in January 2007 from customers with balances greater than $300. Remove duplicate rows in the result.

SELECT EmpNo, EmpFirstName, EmpLastName, EmpPhone

FROM Employee, OrderTbl

WHERE OrdDate=(’01/’AND’/2007’) AND CustBal>300

From the experiment, we firstly connect all the nodes on one side of the array to form an equipotential line and measure it at different points, in order to give a good plot of the potential distribution. Then, in measuring the resistance between the point P and the equipotential via point B, we can conclude that the resistance is between 1kΩ and 2kΩ. While measuring the resistance of the single resistor R in the resistor array, we use the connection as the following diagram:

And from the measurement, we obtain the resistance R by the resistance between point A and B, and then multiply the value by 2; the new value is the actual resistance value of R.

By setting up a model representing one quadrant of the cross-section of a coaxial power cable, the curved equipotential of conductor and sheath using the grid of nodes on the resistor array are approximated. And we can find that the potential for vertical repeat distance from 5 to 14 is gradually increasing. Also, the node potential along AB and CD are 9.83V and 10.04 V. The resistance between the electrodes is 0.397 kΩ.

For the error part, we suggest several recommendations to improve the accuracy of the experiment:

  1. Repeat the procedures several times to obtain more data, and then calculate for the average value.

  2. Do the experiment in a good condition and controlled temperature.

  3. Make sure the good contact of connection wire.

In this experiment, the objective of this experiment was achieved successfully. The modeling of electric and electrostatic fields was analyzed by the use of resistor arrays during the experiment.

From the experiment, we believe that it is related with power transfer. Whenever a source of power with a fixed output impedance such as an electric signal source, a radio transmitter or a mechanical sound (eg, a loudspeaker) operates into a load, the maximum possible power is delivered to the load when the impedance of the load (load impedance or input impedance) is equal to the complex conjugate of the impedance of the source (that is, its internal impedance or output impedance).

Impedance matching is not always necessary. For example, if a source with a low impedance is connected to a load with a high impedance the power that can pass through the connection is limited by the higher impedance. This maximum-voltage connection is a common configuration called impedance bridging or voltage bridging, and is widely used in signal processing. In such applications, delivering a high voltage (to minimize signal degradation during transmission or to consume less power by reducing currents) is often more important than maximum power transfer.

In older audio systems (reliant on transformers and passive filter networks, and based on the telephone system), the source and load resistances were matched at 600 ohms. One reason for this was to maximize power transfer, as there were no amplifiers available that could restore lost signal. Another reason was to ensure correct operation of the hybrid transformers used at central exchange equipment to separate outgoing from incoming speech, so these could be amplified or fed to a four-wire circuit.

Here are two examples.

  1. Telephone systems

. Telephone systems also use matched impedances to minimise echo on long-distance lines This is related to transmission-line theory Matching also enables the telephone hybrid coil. (2 - to 4-wire conversion) to operate correctly As the signals are sent and. received on the same two-wire circuit to the central office (or exchange), cancellation is necessary at the telephone earpiece so excessive sidetone is not heard.

All devices used in telephone signal paths are generally dependent on matched cable, source and load impedances. In the local loop, the impedance chosen is 600 ohms (nominal). Terminating networks are installed at the exchange to offer the best match to their subscriber lines. Each country has its own standard for these networks, but they are all designed to approximate about 600 ohms over the voice frequency band.


Typical push-pull audio tube power amplifier, matched to loudspeaker with an impedance-matching transformer

Audio amplifiers typically do not match impedances, but provide an output impedance that is lower than the load impedance (such as <0.1 ohm in typical semiconductor amplifiers), for improved speaker damping. For vacuum tube amplifiers, impedance-changing transformers are often used to get a low output impedance, and to better match the amplifier's performance to the load impedance.

Some tube amplifiers have output transformer taps to adapt the amplifier output to typical loudspeaker impedances.

The output transformer in vacuum-tube-based amplifiers has two basic functions:

Reducing the output impedance of power pentodes (such as the EL34) in a common-cathode configuration.

The impedance of the loudspeaker on the secondary coil of the transformer will be transformed to a higher impedance on the primary coil in the circuit of the power pentodes by the square of the turns ratio, which forms the impedance scaling factor.

The output stage in common-drain or common-collector semiconductor-based end stages with MOSFETs or power transistors has a very low output impedance. If they are properly balanced, there is no need for a transformer or a large electrolytic capacitor to separate AC from DC current.

Lab Questions

  1. In Access 2007, why can’t the ID field be deleted at the first time after the table is created? What is the usage of this ID field?

  1. What is/are the advantage(s) to define the relationship between the tables in Microsoft Access 2007?

To create queries, forms, and reports to display information from several tables at once.

  1. Consider the following to two tables.






































Thursday, November, 18, 1999



Thursday, November, 18, 1999



Thursday, November, 18, 1999



Friday, November 19, 1999

If a form is created for these two tables (CUS_LNAME, CUS_FNAME, CUS_AREACODE, CUS_PHONE, INV_NUMBER, INV_DATE), is the Form Wizard able to create the subform in this form? Please explain why.

(Assume the relationship is set between these two tables in Access 2007)

No, because a subform is mostly used for 1:M relations.

  1. What is/are the advantage(s) of using Query Design compared with writing SQL statement?

  1. In the Northwind database (of the lab sheet), there are two tables, Products and Categories. We would like to count the number of rows in the Categories table and make the query in the Query Design, like the diagram below.

However, the return of such a query is 77 which is the number of rows in Products table, but not the number of rows in Categories table. Please explain why.

This is because ‘count’ is used in calculations for groups of records, in this case, Categories table and Products table has a relationship (1:M), number of rows in Products table is counted instead of Categories table.

  1. Why do we set the switchboard displays when the database opens?


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