Kayra Ermutlu-030060081 (3rd Week)

Bar Code

A barcode is an optical representation of data that uses a sequence of a predetermined pattern of parallel bars and gaps varying in widths and gap size. Upon reading the barcode by an optical scanner or the barcode reader the sequence can be interpreted numerically and alpha-numerically. Several different types of one-dimensional (1-D) and two-dimensional (2-D) barcodes exist. While 1-D barcodes or linear barcodes use bars and gaps to represent data, 2-D barcodes use geometrical patterns within images such as patterns of dots or squares and are also used frequently.

(Rida A., Yang L., Tentzeris M., RFID-Enabled Sensor Design and Applications, pg.15, Kayra Ermutlu)

Cutting Tool

A cutting tool has one or more sharp cutting edges and is made of a material that is harder than the work material. The cutting edge serves to separate a chip from the parent work material. Connected to the cutting edge are two surfaces od the tool: the rake face and the flank. The rake face, which directs the flow of the newly formed chip, is oriented at a certain angle called the rake angle. It is measured relative to a plane perpendicular to the work surface. The rake angle can be positive or negative. The flank of the tool provides a clearence between the tool and the newly generated work surface, thus protecting the surface from abrasion, which would degrade the finish. This flank surface is oriented at an angle called the relief angle.

(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, 4th Ed., pg. 486, Kayra Ermutlu)

Job Sequence

The job sequence is the order in which jobs are entered on to the production process. This will not however be the order in which they are completed as different jobs will pass through different work stations and will have different process times.

(Greasley A., Operations Management in Business, pg.137, Kayra Ermutlu)

Access Control Protocol

Access control protocols are used in conjunction with channel partitioning techniques in order to allow for the efficient sharing of the medium. The basic operation of an access control protocol is as follows. A packet arriving at the MAC layer from the application layer first undergoes segmentation. It is then packeged into MAC layer frames by adding specific header and trailer information and filling the MAC payload frame. Transmission rules are then applied in order to send the packet to its destination. Since in wireless systems collisions at the receiver cannot be detected by the sender, the status of the reception has tobe communicates back to the sender in the form of an acknowledgement message. In case of an error in the reception, an error correction scheme may be applied in order to recover the packet. Otherwise, the sender is notified to perform a retransmission. At that point, the sender enters a collision resolution phase in order tot ensure a higher probability of success when retansmission is attempted. Bandwidth allocation schemes and schaduling schemes are used to provide fairness either among different users or different traffic types per user.

(Golmie N., Coexistence in Wireless Networks, pg.16, Kayra Ermutlu)