Απαντήσεις στην παραπάνω ερώτηση

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   1-10-14

   googlareto είπε:

   Βρήκα κάποιες ερωτήσεις…και τις παραθέτω όπως τις βρήκα με κάποιες απαντήσεις.Σε γενικές γραμμές ρωτάνε για τη διπλωματική εργασία και κάνουν 1-2ερωτήσεις γενικές,ή της ροής!

   Τι τάση έχει η μπρίζα του σπιτιού μας?
   230/400

   Είδη φίλτρων και λειτουργία τους

   Σχεδιαστε το jk flip flop
   a flip flop has two stable states and thereby is capable of serving as one bit of memory.

   Γραψτε το 23 σε δυαδικη μορφη

   Που μπορουμε να χρησιμοποιησουμε το μετασχηματιστη n=1/1

   Σχεδιαστε το κυκλωμα του UPS
   (Uninterruptible Power Supply) A device that provides battery backup when the electrical power fails or drops to an unacceptable voltage level. Small UPS systems provide power for a few minutes; enough to power down the computer in an orderly manner, while larger systems have enough battery for several hours. In mission critical datacenters, UPS systems are used for just a few minutes until electrical generators take over.

   Θεματα απο ΣΗΕ του στυλ τι ειναι συντελεστης ισχυος, ενεργος αεργος ισχυς κλπ

   Ειδη / τοπολογιες δικτυων

   σχεδιάστε μια κεραία

   ανορθωτής

   τάση από εναλλασσόμενη – συνεχής και σχεδιασμός

   Κατηγοριες γλωσσων προγραμματισμου και ονομαστικη αναφορα μερικων ανα κατηγορια
   1. Λογικός προγραμματισμός: Logical Programming languages operate on facts and relationships from which they can draw a coherent and simple conclusionProlog, ALF, Fril, Gödel, Mercury, Oz, Ciao, Visual Prolog, XSB, and λProlog
   2.Συναρτησιακός προγραμματισμός: Functional programming languages are more closely related to the mathematical concept of `function’ than imperative programming languages. This makes it easier to apply program-proving techniques and logical reasoning to functional programs. In particular, functional programs do not use the concept of variables in the traditional sense, i.e. a memory location whose contents might be changed from time to time as a program executes. ml & Haskell & Lisp (η δεύτερη παλαιότερη γλώσσα υψηλού επιπέδου μετά τη Fortran)
   3.διαδικαστικός / προστακτικός: procedural / imperative programming is associated with languages like C, Fortran, Pascal etc. Imperative programming is distinguished from functional programming in that the former is strongly tied to the concept of variables and memory locations. A variable is associated with a memory location and the contents of that memory location may be changed, via the variable, over the course of time. The meaning or effect of a program fragment at a particular point can only be understood by reference to the current contents of the set of relevant variables, therefore. In contrast, functional programs do not allow the contents of a variable to be changed once set (in simplified terms), hence making them easier to reason about. While languages such as C++ and Java are also imperative programming languages, strictly speaking, they are more commonly referred to as object-oriented programming languages.
   4.παράλληλος προγραμματισμός :ανάπτυξη εφαρμογών που εκμεταλλεύονται την χρήση περισσότερων του ενός επεξεργαστών. Concurrent programming is characterized by programming with more than one process. The main advantage of concurrent programming is that operations can run parallel in it, thus they are much faster than sequential operations. Basically, concurrent programming uses processes and communication to design elegant, responsive and reliable systems.
   5. αντικειμενοστρεφής προγραμματισμός: Object oriented programming is the method of implementing programs which are organized as cooperative collections of objects, and each of which represents an instance of some class, and whose classes are all members of a hierarchy of classes united via inheritance relationships. In these types of programs, classes are generally viewed as static, whereas objects typically have a much more dynamic nature, which is encouraged by the existence of polymorphism. Java, C##,
   6. scripting programming :A scripting language, script language or extension language is a programming language that allows control of one or more software applications. «Scripts» are distinct from the core code of the application, as they are usually written in a different language and are often created or at least modified by the end-user.[1] Scripts are often interpreted from source code orbytecode, whereas the applications they control are traditionally compiled to native machine code PHP, AJAX, JANASCRIPT, PERL, Python, Visual Basic for Applications

   Τι ειναι διαμορφωση και γιατι τη χρησιμοποιουμε
   in electronics, modulation is the process of varying one or more properties of a high frequency periodic waveform, called the carrier signal, with respect to a modulating signal. This is done in a similar fashion as a musician may modulate a tone (a periodic waveform) from a musical instrument by varying its volume, timing and pitch. The three key parameters of a periodic waveform are its amplitude («volume»), itsphase («timing») and its frequency («pitch»), all of which can be modified in accordance with a low frequency signal to obtain the modulated signal. Typically a high-frequency sinusoid waveform is used as carrier signal, but a square wave pulse train may also occur.

   Είναι η μετατροπή ενός μηνύματος σήματος, όπως π.χ. ενός ψηφιακού δυφιορρεύματος (bit stream) ή ενός αναλογικού ακουστικού κύματος σε ένα άλλο σήμα το οποίο μπορεί να μεταδοθεί φυσικά. H διαμόρφωση μιας ημιτονικής κυματομορφής χρησιμοποιείται για την μετατροπή ενός σήματος-μηνύματος ζώνης βάσης σε ένα σήμα βάσης διέλευσης, π.χ. ένα σήμα ραδιοσυχνοτήτων (RF signal). στις ραδιο-επικοινωνίες –cable TV systems or the public switched telephone network – τα ηλεκτρικά σήματα μπορούν να μεταδίδονται μόνο εντός ενός φάσματος συχνοτήτων διέλευσης με συγκεκριμένες συχνότητες κάτω και άνω αποκοπής. διαμορφώνοντας την ημιτονική φέρουσα κυματομορφή μπορούμε να κρατήσουμε την συχνότητα του μεταδιδόμενου σήματος κοντά στο κέντρο συχνοτήτων διέλευσης του φέροντος σήματος . σε συνδυασμό με την αποδιαμόρφωση, η τεχνική αυτή μπορεί να χρησιμοποιηθεί για την μετάδοση ενός σήματος μέσα από κανάλι που είναι αδιαφανές στο εύρος των βασικών συχνοτήτων, όπως π.χ. όταν στέλνουμε ένα τηλεφωνικό σήμα μέσα από οπτικές ίνες.

   modulation, in communications, process in which some characteristic of a wave (the carrier wave) is made to vary in accordance with an information-bearing signal wave (the modulating wave); demodulation is the process by which the original signal is recovered from the wave produced by modulation. The original, unmodulated wave may be of any kind, such as sound or, most often, electromagnetic radiation, including optical waves. The carrier wave can be a direct current, an alternating current, or a pulse chain. In modulation, it is processed in such a way that its amplitude, frequency, or some other property varies.
   Amplitude Modulation
   Amplitude modulation (AM) is the modulation method used in the AM radio broadcast band. In this system the intensity, or amplitude, of the carrier wave varies in accordance with the modulating signal. When the carrier is thus modulated, a fraction of the power is converted to sidebands πλευρικές ζώνες– extending above and below the carrier frequency by an amount equal to the highest modulating frequency. If the modulated carrier is rectified –ανορθωθεί- (see rectifier) and the carrier frequency filtered out, the modulating signal can be recovered. This form of modulation- ΑΜ- is not a very efficient way to send information; the power required is relatively large because the carrier, which contains no information, is sent along with the information.
   In a variant of amplitude modulation, called single sideband modulation (SSB), the modulated signal contains only one sideband and no carrier. The information can be demodulated only if the carrier is used as a reference. This is normally accomplished by generating a wave in the receiver at the carrier frequency. SSB modulation is used for long-distance telephony (such as in the amateur radio bands) and telegraphy over land and submarine cables.
   Frequency and Phase Modulation
   In frequency modulation (FM), the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time. Its principal application is also in radio, where it offers increased noise immunity and decreased distortion over the AM transmissions at the expense of greatly increased bandwidth. The FM band has become the choice of music listeners because of its low-noise, wide-bandwidth qualities; it is also used for the audio portion of a television broadcast.
   Digital radio is based on frequency division multiplexing (FDM), which allows transmission of multiple signals simultaneously over a single transmission path, such as a cable or wireless system. Each signal travels within its own unique frequency range (carrier), which is modulated by the data (audio, video, etc.). Orthogonal frequency-division multiplexing (OFDM) takes this concept further, separating an individual transmission into multiple low-frequency signals with a high resistance to interference. A further extension of the technology, coded orthogonal frequency-division multiplexing (COFDM), is widely used in Europe and elsewhere where the digital audio broadcast (DAB) standard has been adopted. OFDM and COFDM offer the benefits of high spectral efficiency, resilience to radio-frequency (RF) interference, and lower multipath distortion.
   Phase modulation, like frequency modulation, is a form of angle modulation (so called because the angle of the sinewave carrier is changed by the modulating wave). The two methods are very similar in the sense that any attempt to shift the frequency or phase is accomplished by a change in the other.
   Pulse Modulation
   Pulse modulation involves modulating a carrier that is a train of regularly recurrent pulses. The modulation might vary the amplitude (PAM or pulse amplitude modulation), the duration (PDM or pulse duration modulation), or the presence of the pulses (PCM or pulse code modulation). PCM can be used to send digital data; audio signals on a compact disc use pulse code modulation. Developed in 1939 by the English inventor Alec H. Reeves, pulse code modulation is the most important form of pulse modulation because it can be used to transmit information over long distances with hardly any interference or distortion; for this reason it has become increasingly important in the transmission of data in the space program and between computers. Although PCM transmits digital instead of analog signals, the modulating wave is continuous. Digital modulation begins with a digital modulating signal. The two most common digital modulating techniques are phase-shift keying (PSK) and frequency-shift keying (FSK).

   τι είναι οπτικές ίνες και τα πλεονεκτήματά τους
   An optical fiber is a thin, flexible, transparent fiber that acts as a waveguide, or «light pipe», to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune(απρόσβλητες) to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.

   Τι ειναι μοντεμ / λειτουργια του / ποιο ειδος διαμορφωσης χρησιμοποιει (QAM)
   Mόντεμ είναι συσκευή για την μετάδοση και λήψη ψηφιακών δεδομένων μέσω τηλεφωνικών γραμμών επικοινωνιών, διαμορφώνοντας τα ψηφικά δεδομένα σε αναλογικά όπως ακουστικά σήματα και αντίστροφα– για να αποσταλούν μέσω τηλεπικοινωνιακών γραμμών και αποδιαμορφώνοντας τα ακουστικά σήματα σε ψηφιακά δεδομένα για να αποκαλύψει την ψηφιακή πληροφορία. Με την διαμόρφωση/ αποδιαμόρφωση σήματος είναι δυνατό τα υπαρκτά αναλογικά κανάλια επικοινωνιών να υποστηρίζουν ψηφιακές επικοινωνίες όπως email, internet access, fax μεταφορά. ένα κοινό μόντεμ που έχει συνδεθεί με παραδοσιακές γραμμές τηλεφώνου έχει δυνατότητα μετάδοσης 56 kilobits per second, με isdn περίπου διπλάσια μετάδοση ενώ oι καλωδιομένοι διαποδιαμορφωτές και οι dsl γραμμές μπορούν να μεταδίδουν εκατομμύρια bits per second
   cable modem, introduced in the late 1990s. Each of these has a maximum data transfer rate of 1.5 megabits per second. DSL provides a broadband digital communications connection that operates over standard copper telephone wires. The connection requires a DSL modem, which splits transmissions into a lower band for ordinary telephone calls and an upper band for digital data. The drawback of DSL is that connected computers must be within a few miles of the closest transmitting station. A cable modem modulates and demodulates signals like a telephone modem but it transfers data much more quickly over cable lines—primarily fiber-optic or coaxial cable. Broadband over Power Lines (BPL) modems work similarly but utilize electrical lines to transfer data; BPL modems are plugged into electrical outlets. BPL modems may be used to access an Internet service provider over the local power lines, or they may use the wiring within a building to create a network for the computers there.
   Χρησιμοποιεί διαμόρφωση QAM-quadrature amplitude modulation-διαμόρφωση πλάτους με ορθογωνισμό φάσης- a modulation technique that employs both phase modulation (PM) and amplitude modulation (AM). Widely used to transmit digital signals such as digital cable TV and cable Internet service, QAM is also used as the modulation technique in orthogonal frequency division multiplexing The «quadrature» comes from the fact that the phase modulation states are 90 degrees apart from each other.
   Digital QAM
   In digital QAM, the input stream is divided into groups of bits based on the number of modulation states used. For example, in 8QAM, each three bits of input, which provides eight values (0-7) alters the phase and amplitude of the carrier to derive eight unique modulation states (4 phases * 2amplitutes ) In 64QAM, each six bits generates 64 modulation states; in 128QAM, each seven bits generates 128 states, and so on. In this 8QAM example, three bits of input generate eight different modulation states (0-7) using four phase angles on 90 degree boundaries and two amplitudes: one at 50% modulation; the other at 100% (4 phases X 2 amplitudes = 8 modulation states).
   Τι ειναι συναρτηση μεταφορας, τι ειναι ευσταθεια , ποτε ενα συστημα ειναι ευσταθες

   Αν ενας θερμοσιφωνας εχει ισχυ 2000W τι ασφαλεια πρεπει να βαλω στον πινακα ?
   10 ή 15 Α

   Τι ασφάλεια βάζουμε στο φωτισμό? 10Α

   Αν θελω να μεταφερω φωνη απο Αθηνα στη Θεσσαλονικη να χρησιμοποιησω ενσυρματο η ασυρματο τροπο και γιατι (γενικος σχολιασμος επι των πλεονεκτηματων καθε τροπου)

   τι ειναι το ΑΝΑΔΕΛΤA

   τι ειναι κυματοδηγος

   Απάντηση

   +62

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