1 SAMPLE QUESTIONS FOR PhD QUALIFYING EXAMINATION CS 6352-Performance Computer Networks 1. Into a single queue with unlimited buffer size, customers always arrive in pairs but line up one after another in the waiting line for service. One of an arriving pair joins the line ahead of the other, by a random choice. The single server takes up one customer at a time from the head of the queue and serves. Each customer leaves immediately upon completion of his/her service (that is, without waiting for the completion of the partner’s service). Arrivals of pairs are Poisson with a rate of 1 pair per hour. Service times of individual customers are independent and identically distributed Exponential random variables with a mean of 0.25 hour for each customer (and not for a pair). Determine the expected response time of an individual customer. 2. Consider a two-processor server where each processor in enabled with technology that allows the processors to operate at a higher speed under heavy loads, and to operate at a reduced speed under low loads to conserve power. Users submit jobs according to a Poisson process with rate jobs per second. If there is one job in the system, only a single processor is busy, and the processor operates at a speed of 500 MHz (500 million cycles per second). If there are two jobs in the system, both processors are busy, and each operates at a speed of 1000 MHz. If there are three or more jobs in the system, both processors are busy, and each processor operates at a speed of 1500 MHz. The length of a job is modeled as exponentially distributed and requires an average of 500 million CPU cycles. Buffer size is unlimited. (a) Draw the state diagram for the system, clearly labeling transition rates. (b) Find the steady-state probabilities for the number of jobs in the system. (c) Find the condition for in order for the system to be stable. CS 6353-Compiler Construction Syntax Analysis Explain why the following grammar is LALR(1) but not SLR(1). S a|bAc|dc|bda A d Intermediate Code Generation Give a syntax-directed translation scheme for the while-loop, i.e. Rule1 while (E1) do S1; { define your action here } The while-loop has the common meaning and you can use either two pass approach or back-patching. Synthesized attributes can be defined as necessary. In addition, there are two predefined functions as follows: newlabel(): return an unused new label L. gen(X): generate three address code as indicated by X. CS 6354-Software Engineering2 System Description Consider a system for maintaining patient records in a doctor’s office. The system should allow the user to create records for new patients, update the information, and delete patient records. The system should also generate billing information for insurance companies, record payments from the companies and patients, generate bills for patients, and send reminders to patients regarding follow-up treatments. For each patient, the system stores the name, social security number, date of birth, address, and telephone number of the patient as well as the patient’s insurance company, employer, and name of parent or guardian (if under 18 years), name of spouse (if married). The system also maintains the medical history of each patient, including the date of each visit, the diagnosis, prescribed treatment, duration of treatment, and the result. The system must enable the user to perform the following functions: 1. For adding a new patient to the system, the user fills out a form containing the patient information and submits it to the system. Various validation checks are performed by the system (duplicate name, reasonable age, correct insurance company, etc.) and the record is accepted only if it passes these checks. The user can also delete patient records. 2. For updating the record of a patient, the user fills out or updates the information (including date of visit, diagnosis, total charge, patient and insurance payments, change of address, etc.). The system accepts the updates if the validation checks are passed. 3. If the user wishes to generate bills for insurance companies, the system goes through all the patient records and generates bills for new payments or payments that are past the due date. Letters and addresses are prepared and printed. 4. Similarly, the user can generate bills for patients as well as send reminders for patients who need follow-up treatment. 1. Requirements elicitation and analysis. (i) Draw a Use Case diagram showing the functions of the system. Show the system boundary, use case(s), and actors. 2. Requirements analysis. (i) Consider the following entity classes: PatientRecordSystem (keeps track of the information about all the patients in the system); CompanyInfo (name, address of the company and the name and telephone number of a point of contact); Date (month, day, year); Status (information about the status of the patient, including starting treatment, continuing treatment, recovered, etc.); History (keeps information for each visit by a patient); PatientInfo (name, address, telephone number, parent/guardian info, date of birth, social security number, marital status and spouse’s info, history, employer, insurance company); PersonInfo (name, address, telephone number), VisitInfo (date, problem description, diagnosis, prescribed treatment, duration - start & end dates, status, payment info); PaymentInfo (responsible party, amount billed, amount paid); Draw the Class diagram. Use all the classes listed above and do not use any classes not listed above. Show all the associations, inheritances, aggregations, multiplicities, and roles.3 3. Consider an issue that arises in the implementation of the database for the patient information system, namely, how to implement the database subsystem. Give details of the following rationale management scenario that might arise (give concise answers in English, not UML, with just a few sentences in the space provided here). (a) State the problem. (b) Identify some proposals (c) Give some evaluation criterion (criteria). (d) Give some arguments. (e) Describe the resolution. (f) List possible action items
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