Rozprawy doktorskie: „Collaborative Research Center 912”

1

Kissinger, Thomas, Benjamin Schlegel, Dirk Habich i Wolfgang Lehner. "QPPT: Query Processing on Prefix Trees". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-113269.

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Modern database systems have to process huge amounts of data and should provide results with low latency at the same time. To achieve this, data is nowadays typically hold completely in main memory, to benefit of its high bandwidth and low access latency that could never be reached with disks. Current in-memory databases are usually columnstores that exchange columns or vectors between operators and suffer from a high tuple reconstruction overhead. In this paper, we present the indexed table-at-a-time processing model that makes indexes the first-class citizen of the database system. The processing model comprises the concepts of intermediate indexed tables and cooperative operators, which make indexes the common data exchange format between plan operators. To keep the intermediate index materialization costs low, we employ optimized prefix trees that offer a balanced read/write performance. The indexed tableat-a-time processing model allows the efficient construction of composed operators like the multi-way-select-join-group. Such operators speed up the processing of complex OLAP queries so that our approach outperforms state-of-the-art in-memory databases.

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2

Baier, Christel, Benjamin Engel, Sascha Klüppelholz, Steffen Märcker, Hendrik Tews i Marcus Völp. "A Probabilistic Quantitative Analysis of Probabilistic-Write/Copy-Select". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-129917.

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Probabilistic-Write/Copy-Select (PWCS) is a novel synchronization scheme suggested by Nicholas Mc Guire which avoids expensive atomic operations for synchronizing access to shared objects. Instead, PWCS makes inconsistencies detectable and recoverable. It builds on the assumption that, for typical workloads, the probability for data races is very small. Mc Guire describes PWCS for multiple readers but only one writer of a shared data structure. In this paper, we report on the formal analysis of the PWCS protocol using a continuous-time Markov chain model and probabilistic model checking techniques. Besides the original PWCS protocol, we also considered a variant with multiple writers. The results were obtained by the model checker PRISM and served to identify scenarios in which the use of the PWCS protocol is justified by guarantees on the probability of data races. Moreover, the analysis showed several other quantitative properties of the PWCS protocol.

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3

Pfennig, Stefan, i Elke Franz. "Secure Network Coding: Dependency of Efficiency on Network Topology". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-128456.

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Network Coding is a new possibility to transmit data through a network. By combining different packets instead of simply forwarding, network coding offers the opportunity to reach the Min-Cut/Max-Flow capacity in multicast data transmissions. However, the basic schemes are vulnerable to so-called pollution attacks, where an attacker can jam large parts of the transmission by infiltrating only one bogus message. In the literature we found several approaches which aim at handling this kind of attack with different amounts of overhead. Though, the cost for a specific secure network coding scheme highly depends on the underlying network. The goal of this paper is on the one hand to describe which network parameters influence the efficiency of a certain scheme and on the other hand to provide concrete suggestions for selecting the most efficient secure network coding scheme considering a given network. We will illustrate that there does not exist “the best” secure network scheme concerning efficiency, but all selected schemes are more or less suited under certain network topologies.

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4

Hähnel, Marcus, Björn Döbel, Marcus Völp i Hermann Härtig. "Measuring energy consumption for short code paths using RAPL". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-113258.

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Measuring the energy consumption of software components is a major building block for generating models that allow for energy-aware scheduling, accounting and budgeting. Current measurement techniques focus on coarse-grained measurements of application or system events. However, fine grain adjustments in particular in the operating-system kernel and in application-level servers require power profiles at the level of a single software function. Until recently, this appeared to be impossible due to the lacking fine grain resolution and high costs of measurement equipment. In this paper we report on our experience in using the Running Average Power Limit (RAPL) energy sensors available in recent Intel CPUs for measuring energy consumption of short code paths. We investigate the granularity at which RAPL measurements can be performed and discuss practical obstacles that occur when performing these measurements on complex modern CPUs. Furthermore, we demonstrate how to use the RAPL infrastructure to characterize the energy costs for decoding video slices.

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5

Engelmann, Sabrina, Zuleita K. M. Ho i Eduard A. Jorswieck. "Interference Leakage Neutralization in Two-Hop Wiretap Channels with Partial CSI". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-128438.

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In this paper, we analyze the four-node relay wiretap channel, where the relay performs amplify-and-forward. There is no direct link between transmitter and receiver available. The transmitter has multiple antennas, which assist in securing the transmission over both phases. In case of full channel state information (CSI), the transmitter can apply information leakage neutralization in order to prevent the eavesdropper from obtaining any information about the signal sent. This gets more challenging, if the transmitter has only an outdated estimate of the channel from the relay to the eavesdropper. For this case, we optimize the worst case secrecy rate by choosing intelligently the beamforming vectors and the power allocation at the transmitter and the relay.

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6

Lehner, Wolfgang. "Energy-Efficient In-Memory Database Computing". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-115547.

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The efficient and flexible management of large datasets is one of the core requirements of modern business applications. Having access to consistent and up-to-date information is the foundation for operational, tactical, and strategic decision making. Within the last few years, the database community sparked a large number of extremely innovative research projects to push the envelope in the context of modern database system architectures. In this paper, we outline requirements and influencing factors to identify some of the hot research topics in database management systems. We argue that—even after 30 years of active database research—the time is right to rethink some of the core architectural principles and come up with novel approaches to meet the requirements of the next decades in data management. The sheer number of diverse and novel (e.g., scientific) application areas, the existence of modern hardware capabilities, and the need of large data centers to become more energy-efficient will be the drivers for database research in the years to come.

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7

Fettweis, Gerhard P., Hassan Najeeb ul, Lukas Landau i Erik Fischer. "Wireless Interconnect for Board and Chip Level". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-118302.

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Electronic systems of the future require a very high bandwidth communications infrastructure within the system. This way the massive amount of compute power which will be available can be inter-connected to realize future powerful advanced electronic systems. Today, electronic inter-connects between 3D chip-stacks, as well as intra-connects within 3D chip-stacks are approaching data rates of 100 Gbit/s soon. Hence, the question to be answered is how to efficiently design the communications infrastructure which will be within electronic systems. Within this paper approaches and results for building this infrastructure for future electronics are addressed.

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8

Pfennig, Stefan, i Elke Franz. "Comparison of Different Secure Network Coding Paradigms Concerning Transmission Efficiency". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-145096.

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Preventing the success of active attacks is of essential importance for network coding since even the infiltration of one single corrupted data packet can jam large parts of the network. The existing approaches for network coding schemes preventing such pollution attacks can be divided into two categories: utilize cryptographic approaches or utilize redundancy similar to error correction coding. Within this paper, we compared both paradigms concerning efficiency of data transmission under various circumstances. Particularly, we considered an attacker of a certain strength as well as the influence of the generation size. The results are helpful for selecting a suitable approach for network coding taking into account both security against pollution attacks and efficiency.

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9

Baier, Christel, Marcus Daum, Benjamin Engel, Hermann Härtig, Joachim Klein, Sascha Klüppelholz, Steffen Märcker, Hendrik Tews i Marcus Völp. "Chiefly Symmetric: Results on the Scalability of Probabilistic Model Checking for Operating-System Code". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121319.

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Reliability in terms of functional properties from the safety-liveness spectrum is an indispensable requirement of low-level operating-system (OS) code. However, with evermore complex and thus less predictable hardware, quantitative and probabilistic guarantees become more and more important. Probabilistic model checking is one technique to automatically obtain these guarantees. First experiences with the automated quantitative analysis of low-level operating-system code confirm the expectation that the naive probabilistic model checking approach rapidly reaches its limits when increasing the numbers of processes. This paper reports on our work-in-progress to tackle the state explosion problem for low-level OS-code caused by the exponential blow-up of the model size when the number of processes grows. We studied the symmetry reduction approach and carried out our experiments with a simple test-and-test-and-set lock case study as a representative example for a wide range of protocols with natural inter-process dependencies and long-run properties. We quickly see a state-space explosion for scenarios where inter-process dependencies are insignificant. However, once inter-process dependencies dominate the picture models with hundred and more processes can be constructed and analysed.

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10

Pfennig, Stefan, i Elke Franz. "Comparison of Different Secure Network Coding Paradigms Concerning Transmission Efficiency". Technische Universität Dresden, 2013. https://tud.qucosa.de/id/qucosa%3A28134.

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Preventing the success of active attacks is of essential importance for network coding since even the infiltration of one single corrupted data packet can jam large parts of the network. The existing approaches for network coding schemes preventing such pollution attacks can be divided into two categories: utilize cryptographic approaches or utilize redundancy similar to error correction coding. Within this paper, we compared both paradigms concerning efficiency of data transmission under various circumstances. Particularly, we considered an attacker of a certain strength as well as the influence of the generation size. The results are helpful for selecting a suitable approach for network coding taking into account both security against pollution attacks and efficiency.

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11

Kissinger, Thomas, Benjamin Schlegel, Matthias Böhm, Dirk Habich i Wolfgang Lehner. "A high-throughput in-memory index, durable on flash-based SSD". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105947.

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Growing memory capacities and the increasing number of cores on modern hardware enforces the design of new in-memory indexing structures that reduce the number of memory transfers and minimizes the need for locking to allow massive parallel access. However, most applications depend on hard durability constraints requiring a persistent medium like SSDs, which shorten the latency and throughput gap between main memory and hard disks. In this paper, we present our winning solution of the SIGMOD Programming Contest 2011. It consists of an in-memory indexing structure that provides a balanced read/write performance as well as non-blocking reads and single-lock writes. Complementary to this index, we describe an SSD-optimized logging approach to fit hard durability requirements at a high throughput rate.

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12

Baier, Christel, Marcus Daum, Benjamin Engel, Hermann Härtig, Joachim Klein, Sascha Klüppelholz, Steffen Märcker, Hendrik Tews i Marcus Völp. "Chiefly Symmetric: Results on the Scalability of Probabilistic Model Checking for Operating-System Code". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A27132.

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Reliability in terms of functional properties from the safety-liveness spectrum is an indispensable requirement of low-level operating-system (OS) code. However, with evermore complex and thus less predictable hardware, quantitative and probabilistic guarantees become more and more important. Probabilistic model checking is one technique to automatically obtain these guarantees. First experiences with the automated quantitative analysis of low-level operating-system code confirm the expectation that the naive probabilistic model checking approach rapidly reaches its limits when increasing the numbers of processes. This paper reports on our work-in-progress to tackle the state explosion problem for low-level OS-code caused by the exponential blow-up of the model size when the number of processes grows. We studied the symmetry reduction approach and carried out our experiments with a simple test-and-test-and-set lock case study as a representative example for a wide range of protocols with natural inter-process dependencies and long-run properties. We quickly see a state-space explosion for scenarios where inter-process dependencies are insignificant. However, once inter-process dependencies dominate the picture models with hundred and more processes can be constructed and analysed.

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13

Hassan, Najeeb ul, Ali E. Pusane, Michael Lentmaier, Gerhard P. Fettweis i Daniel J. Costello. "Reduced Complexity Window Decoding Schedules for Coupled LDPC Codes". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105936.

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Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.

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14

Richter, Johannes, Elke Franz, Sabrina Engelmann, Stefan Pfennig i Eduard A. Jorswieck. "Physical Layer Security vs. Network Layer Secrecy: Who Wins on the Untrusted Two-Way Relay Channel?" Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-145086.

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We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.

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15

Kissinger, Thomas, Benjamin Schlegel, Matthias Böhm, Dirk Habich i Wolfgang Lehner. "A high-throughput in-memory index, durable on flash-based SSD: Insights into the winning solution of the SIGMOD programming contest 2011". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26635.

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Growing memory capacities and the increasing number of cores on modern hardware enforces the design of new in-memory indexing structures that reduce the number of memory transfers and minimizes the need for locking to allow massive parallel access. However, most applications depend on hard durability constraints requiring a persistent medium like SSDs, which shorten the latency and throughput gap between main memory and hard disks. In this paper, we present our winning solution of the SIGMOD Programming Contest 2011. It consists of an in-memory indexing structure that provides a balanced read/write performance as well as non-blocking reads and single-lock writes. Complementary to this index, we describe an SSD-optimized logging approach to fit hard durability requirements at a high throughput rate.

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16

Krone, Stefan, i Gerhard Fettweis. "Capacity of Communications Channels with 1-Bit Quantization and Oversampling at the Receiver". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-101462.

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Communications receivers that rely on 1-bit analogto-digital conversion are advantageous in terms of hardware complexity and power dissipation. Performance limitations due to the 1-bit quantization can be tackled with oversampling. This paper considers the oversampling gain from an information-theoretic perspective by analyzing the channel capacity with 1-bit quantization and oversampling at the receiver for the particular case of AWGN channels. This includes a numerical computation of the capacity and optimal transmit symbol constellations, as well as the derivation of closed-form expressions for large oversampling ratios and for high signal-to-noise ratios of the channel.

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17

Baier, Christel, Marcus Daum, Benjamin Engel, Hermann Härtig, Joachim Klein, Sascha Klüppelholz, Steffen Märcker, Hendrik Tews i Marcus Völp. "Waiting for Locks: How Long Does It Usually Take?" Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121259.

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Reliability of low-level operating-system (OS) code is an indispensable requirement. This includes functional properties from the safety-liveness spectrum, but also quantitative properties stating, e.g., that the average waiting time on locks is sufficiently small or that the energy requirement of a certain system call is below a given threshold with a high probability. This paper reports on our experiences made in a running project where the goal is to apply probabilistic model checking techniques and to align the results of the model checker with measurements to predict quantitative properties of low-level OS code.

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18

Richter, Johannes, Elke Franz, Sabrina Engelmann, Stefan Pfennig i Eduard A. Jorswieck. "Physical Layer Security vs. Network Layer Secrecy: Who Wins on the Untrusted Two-Way Relay Channel?" Technische Universität Dresden, 2013. https://tud.qucosa.de/id/qucosa%3A28133.

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We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.

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19

Ho, Zuleita K. M., i Eduard Jorswieck. "Secure degrees of freedom on widely linear instantaneous relay-assisted interference channel". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-128420.

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The number of secure data streams a relay-assisted interference channel can support has been an intriguing problem. The problem is not solved even for a fundamental scenario with a single antenna at each transmitter, receiver and relay. In this paper, we study the achievable secure degrees of freedom of instantaneous relay-assisted interference channels with real and complex coefficients. The study of secure degrees of freedom with complex coefficients is not a trivial multiuser extension of the scenarios with real channel coefficients as in the case for the degrees of freedom, due to secrecy constraints. We tackle this challenge by jointly designing the improper transmit signals and widely-linear relay processing strategies.

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20

Jorswieck, Eduard A., Anne Wolf i Sabrina Engelmann. "Secret key generation from reciprocal spatially correlated MIMO channels". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-143998.

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Secret key generation from reciprocal multi-antenna channels is an interesting alternative to cryptographic key management in wireless systems without infrastructure access. In this work, we study the secret key rate for the basic source model with a MIMO channel. First, we derive an expression for the secret key rate under spatial correlation modelled by the Kronecker model and with spatial precoding at both communication nodes. Next, we analyze the result for uncorrelated antennas to understand the optimal precoding for this special case, which is equal power allocation. Then, the impact of correlation is characterized using Majorization theory. Surprisingly for small SNR, spatial correlation increases the secret key rate. For high SNR, the maximum secret key rate is achieved for uncorrelated antennas. The results indicate that a solid system design for reciprocal MIMO key generation is required to establish the secret key rate gains.

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21

Baier, Christel, Marcus Daum, Benjamin Engel, Hermann Härtig, Joachim Klein, Sascha Klüppelholz, Steffen Märcker, Hendrik Tews i Marcus Völp. "Waiting for Locks: How Long Does It Usually Take?" Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A27128.

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Reliability of low-level operating-system (OS) code is an indispensable requirement. This includes functional properties from the safety-liveness spectrum, but also quantitative properties stating, e.g., that the average waiting time on locks is sufficiently small or that the energy requirement of a certain system call is below a given threshold with a high probability. This paper reports on our experiences made in a running project where the goal is to apply probabilistic model checking techniques and to align the results of the model checker with measurements to predict quantitative properties of low-level OS code.

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22

Ho, Zuleita K. M., Eduard A. Jorswieck i Sabrina Engelmann. "Efficient information leakage neutralization on a relay-assisted multi-carrier interference channel". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-128447.

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In heterogeneous dense networks where spectrum is shared, users privacy remains one of the major challenges. When the receivers are not only interested in their own signals but also in eavesdropping other users' signals, the cross talk becomes information leakage.We propose a novel and efficient secrecy rate enhancing relay strategy EFFIN for information leakage neutralization. The relay matrix is chosen such that the effective leakage channel (spectral and spatial) is zero. Thus, it ensures secrecy regardless of receive processing employed at eavesdroppers and does not rely on wiretaps codes to ensure secrecy, unlike other physical layer security techniques such as artificial noise. EFFIN achieves a higher sum secrecy rate over several state-of-the-art baseline methods.

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23

Krone, Stefan, i Gerhard Fettweis. "Communications with 1-Bit Quantization and Oversampling at the Receiver: Benefiting from Inter-Symbol-Interference". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-101473.

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1-bit analog-to-digital conversion is very attractive for low-complexity communications receivers. A major drawback is, however, the small spectral efficiency when sampling at symbol rate. This can be improved through oversampling by exploiting the signal distortion caused by the transmission channel. This paper analyzes the achievable data rate of band-limited communications channels that are subject to additive noise and inter-symbol-interference with 1-bit quantization and oversampling at the receiver. It is shown that not only the channel noise but also the inter-symbol-interference can be exploited to benefit from oversampling.

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24

Hassan, Najeeb ul, Ali E. Pusane, Michael Lentmaier, Gerhard P. Fettweis i Daniel J. Costello. "Reduced Complexity Window Decoding Schedules for Coupled LDPC Codes". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26634.

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Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.

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25

Fernández-Díaz, Álvaro, Christel Baier, Clara Benac-Earle i Lars-Åke Fredlund. "Static Partial Order Reduction for Probabilistic Concurrent Systems". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121261.

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Sound criteria for partial order reduction for probabilistic concurrent systems have been presented in the literature. Their realization relies on a depth-first search-based approach for generating the reduced model. The drawback of this dynamic approach is that it can hardly be combined with other techniques to tackle the state explosion problem, e.g., symbolic probabilistic model checking with multi-terminal variants of binary decision diagrams. Following the approach presented by Kurshan et al. for non-probabilistic systems, we study partial order reduction techniques for probabilistic concurrent systems that can be realized by a static analysis. The idea is to inject the reduction criteria into the control flow graphs of the processes of the system to be analyzed. We provide the theoretical foundations of static partial order reduction for probabilistic concurrent systems and present algorithms to realize them. Finally, we report on some experimental results.

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26

Jorswieck, Eduard A., Anne Wolf i Sabrina Engelmann. "Secret key generation from reciprocal spatially correlated MIMO channels". Technische Universität Dresden, 2013. https://tud.qucosa.de/id/qucosa%3A28101.

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Secret key generation from reciprocal multi-antenna channels is an interesting alternative to cryptographic key management in wireless systems without infrastructure access. In this work, we study the secret key rate for the basic source model with a MIMO channel. First, we derive an expression for the secret key rate under spatial correlation modelled by the Kronecker model and with spatial precoding at both communication nodes. Next, we analyze the result for uncorrelated antennas to understand the optimal precoding for this special case, which is equal power allocation. Then, the impact of correlation is characterized using Majorization theory. Surprisingly for small SNR, spatial correlation increases the secret key rate. For high SNR, the maximum secret key rate is achieved for uncorrelated antennas. The results indicate that a solid system design for reciprocal MIMO key generation is required to establish the secret key rate gains.

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27

Gerbracht, Sabrina, Eduard A. Jorswieck, Gan Zheng i Björn Ottersten. "Non-regenerative Two-Hop Wiretap Channels using Interference Neutralization". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-113245.

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In this paper, we analyze the achievable secrecy rates in the two-hop wiretap channel with four nodes, where the transmitter and the receiver have multiple antennas while the relay and the eavesdropper have only a single antenna each. The relay is operating in amplify-and-forward mode and all the channels between the nodes are known perfectly by the transmitter. We discuss different transmission and protection schemes like artificial noise (AN). Furthermore, we introduce interference neutralization (IN) as a new protection scheme. We compare the different schemes regarding the high-SNR slope and the high-SNR power offset and illustrate the performance by simulation results. It is shown analytically as well as by numerical simulations that the high SNR performance of the proposed IN scheme is better than the one of AN.

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28

Krone, Stefan, i Gerhard Fettweis. "Capacity of Communications Channels with 1-Bit Quantization and Oversampling at the Receiver". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26361.

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Communications receivers that rely on 1-bit analogto-digital conversion are advantageous in terms of hardware complexity and power dissipation. Performance limitations due to the 1-bit quantization can be tackled with oversampling. This paper considers the oversampling gain from an information-theoretic perspective by analyzing the channel capacity with 1-bit quantization and oversampling at the receiver for the particular case of AWGN channels. This includes a numerical computation of the capacity and optimal transmit symbol constellations, as well as the derivation of closed-form expressions for large oversampling ratios and for high signal-to-noise ratios of the channel.

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29

Fernández-Díaz, Álvaro, Christel Baier, Clara Benac-Earle i Lars-Åke Fredlund. "Static Partial Order Reduction for Probabilistic Concurrent Systems". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26083.

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Sound criteria for partial order reduction for probabilistic concurrent systems have been presented in the literature. Their realization relies on a depth-first search-based approach for generating the reduced model. The drawback of this dynamic approach is that it can hardly be combined with other techniques to tackle the state explosion problem, e.g., symbolic probabilistic model checking with multi-terminal variants of binary decision diagrams. Following the approach presented by Kurshan et al. for non-probabilistic systems, we study partial order reduction techniques for probabilistic concurrent systems that can be realized by a static analysis. The idea is to inject the reduction criteria into the control flow graphs of the processes of the system to be analyzed. We provide the theoretical foundations of static partial order reduction for probabilistic concurrent systems and present algorithms to realize them. Finally, we report on some experimental results.

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30

Hassan, Najeeb ul, Michael Lentmaier i Gerhard P. Fettweis. "Comparison of LDPC Block and LDPC Convolutional Codes based on their Decoding Latency". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-101450.

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We compare LDPC block and LDPC convolutional codes with respect to their decoding performance under low decoding latencies. Protograph based regular LDPC codes are considered with rather small lifting factors. LDPC block and convolutional codes are decoded using belief propagation. For LDPC convolutional codes, a sliding window decoder with different window sizes is applied to continuously decode the input symbols. We show the required Eb/N0 to achieve a bit error rate of 10 -5 for the LDPC block and LDPC convolutional codes for the decoding latency of up to approximately 550 information bits. It has been observed that LDPC convolutional codes perform better than the block codes from which they are derived even at low latency. We demonstrate the trade off between complexity and performance in terms of lifting factor and window size for a fixed value of latency. Furthermore, the two codes are also compared in terms of their complexity as a function of Eb/N0. Convolutional codes with Viterbi decoding are also compared with the two above mentioned codes.

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31

Krone, Stefan, i Gerhard Fettweis. "Communications with 1-Bit Quantization and Oversampling at the Receiver: Benefiting from Inter-Symbol-Interference". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26362.

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1-bit analog-to-digital conversion is very attractive for low-complexity communications receivers. A major drawback is, however, the small spectral efficiency when sampling at symbol rate. This can be improved through oversampling by exploiting the signal distortion caused by the transmission channel. This paper analyzes the achievable data rate of band-limited communications channels that are subject to additive noise and inter-symbol-interference with 1-bit quantization and oversampling at the receiver. It is shown that not only the channel noise but also the inter-symbol-interference can be exploited to benefit from oversampling.

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32

Gerbracht, Sabrina, Eduard A. Jorswieck, Gan Zheng i Björn Ottersten. "Non-regenerative Two-Hop Wiretap Channels using Interference Neutralization". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26894.

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In this paper, we analyze the achievable secrecy rates in the two-hop wiretap channel with four nodes, where the transmitter and the receiver have multiple antennas while the relay and the eavesdropper have only a single antenna each. The relay is operating in amplify-and-forward mode and all the channels between the nodes are known perfectly by the transmitter. We discuss different transmission and protection schemes like artificial noise (AN). Furthermore, we introduce interference neutralization (IN) as a new protection scheme. We compare the different schemes regarding the high-SNR slope and the high-SNR power offset and illustrate the performance by simulation results. It is shown analytically as well as by numerical simulations that the high SNR performance of the proposed IN scheme is better than the one of AN.

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Hall, William D. (William David) 1968. "Efficient capacity allocation in a collaborative air transportation system". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/8786.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, Operations Research Center, 1999.
Includes bibliographical references (p. 177-180).
This thesis proposes methods of allocating airport capacity to the users of the National Airspace System (NAS) during periods in which demand for the resources exceeds capacity. A metric by which the proposed methods are judged is the value that the users of the N AS are able to realize through the allocation. Maximization of this metric produces notably different results from minimization of flight-minutes of delay and similar objectives employed in related works. The heart of this approach is the treatment of the Federal Aviation Administration (FAA) and the NAS users as solvers of subproblems in a decomposition of the overall problem of determining how to operate the system. The best possible capacity allocation method would allow the users, to achieve the same result collectively that a single omniscient entity in control of all decisions in the system could achieve. The typical approach to decomposition employed in optimization, that of modifying the subproblem objectives through a penalty function determined by a master "dual" problem, is employed in the Objective-Based Allocation Method (OBAM). It is shown that the proper choice of penalty function results in a method that performs well dynamically and, assuming each user operates to maximize its operating objectives through the allocation, achieves the optimal solution that an omniscient single controller would achieve. OBAM requires complete communication of user objectives and constraints to achieve optimality. It also requires that the penalty functions used to coordinate the subproblem solutions be added to the user objective functions through assessment of fees. The second part of this thesis addresses the improvement of the decomposition by changing the nature of the allocation without these requirements. Rather than allocate airport arrival capacity alone, a more general notion of airport capacity that captures the interactions between arrival and departure processes at an airport is allocated. This allows the users the flexibility to adjust the operations mix of the airport according to their objectives and improves the ability of the system to match demand to forecast airport capacity. Through simulation, it is shown that this approach could improve significantly on the primary metric of achieving user value. In addition, the approach facilitates side benefits, such as the reduction of fuel consumption, the reduction of harmful emissions into the environment, and the improvement of service reliability for the flying public.
by William D. Hall.
Ph.D.

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Malasky, Jeremy S. "Human machine collaborative decision making in a complex optimization system". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32514.

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Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2005.
Includes bibliographical references (p. 149-151).
Numerous complex real-world applications are either theoretically intractable or unable to be solved in a practical amount of time. Researchers and practitioners are forced to implement heuristics in solving such problems that can lead to highly sub-optimal solutions. Our research focuses on inserting a human "in-the-loop" of the decision-making or problem solving process in order to generate solutions in a timely manner that improve upon those that are generated either scolely by a human or solely by a computer. We refer to this as Human-Machine Collaborative Decision-Making (HMCDM). The typical design process for developing human-machine approaches either starts with a human approach and augments it with decision-support or starts with an automated approach and augments it with operator input. We provide an alternative design process by presenting an 1HMCDM methodology that addresses collaboration from the outset of the design of the decision- making approach. We apply this design process to a complex military resource allocation and planning problem which selects, sequences, and schedules teams of unmanned aerial vehicles (UAVs) to perform sensing (Intelligence, Surveillance, and Reconnaissance - ISR) and strike activities against enemy targets. Specifically, we examined varying degrees of human-machine collaboration in the creation of variables in the solution of this problem. We also introduce an IIHMCDM method that combines traditional goal decomposition with a model formulation into an Iterative Composite Variable Approach for solving large-scale optimization problems.
(cont.) Finally, we show through experimentation the potential for improvement in the quality and speed of solutions that can be achieved through the use of an HMCDM approach.
by Jeremy S. Malasky.
S.M.

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35

Hassan, Najeeb ul, Michael Lentmaier i Gerhard P. Fettweis. "Comparison of LDPC Block and LDPC Convolutional Codes based on their Decoding Latency". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26359.

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We compare LDPC block and LDPC convolutional codes with respect to their decoding performance under low decoding latencies. Protograph based regular LDPC codes are considered with rather small lifting factors. LDPC block and convolutional codes are decoded using belief propagation. For LDPC convolutional codes, a sliding window decoder with different window sizes is applied to continuously decode the input symbols. We show the required Eb/N0 to achieve a bit error rate of 10 -5 for the LDPC block and LDPC convolutional codes for the decoding latency of up to approximately 550 information bits. It has been observed that LDPC convolutional codes perform better than the block codes from which they are derived even at low latency. We demonstrate the trade off between complexity and performance in terms of lifting factor and window size for a fixed value of latency. Furthermore, the two codes are also compared in terms of their complexity as a function of Eb/N0. Convolutional codes with Viterbi decoding are also compared with the two above mentioned codes.

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36

Wendisch, Manfred, Marlen Brückner, John P. Burrows, Susanne Crewell, Klaus Dethloff, Kerstin Ebell, Christof Lüpkes i in. "Introduction of the Transregional Collaborative Research Center TR 172: Arctic Amplification". Universität Leipzig, 2017. https://ul.qucosa.de/id/qucosa%3A16739.

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A new German research consortium is investigating the causes and effects of the rapid rise of near-surface air temperatures in the Artic. Within the last 25 years a remarkable increase of the Arctic near-surface air temperature exceeding the global warming by a factor of two to three has been observed. The phenomenon is commonly referred to as Arctic Amplification. The warming results in rather drastic changes of a variety of climate parameters. For example, the Arctic sea ice has declined significantly. This ice retreat has been well identified by satellite measurements. However, coupled regional and global climate models still fail to reproduce it adequately; they tend to systematically underestimate the observed sea ice decline. This model observation difference implies that the underlying physical processes and feedback mechanisms are not appropriately represented in Arctic climate models. Thus, the predictions of these models are also likely to be inadequate. It is mandatory to identify the origin of this disagreement.
Ein neu geschaffenes deutsches Forschungskonsortium untersucht die Ursachen und Effekte des rapiden Anstiegs der bodennahen Lufttemperatur in der Arktis. Innerhalb der letzten 25 Jahre wurde ein bemerkenswerter Anstieg der Bodenlufttemperatur in der Arktis beobachtet, welcher die globale Erwärmung um den Faktor 2 bis 3 übersteigt. Dieses Phänomen wird als arktische Verstärkung bezeichnet. Diese Erwärmung resultiert vielmehr in einer drastischen Änderung einer Vielzahl von Klimarparametern. Beispielsweise ist das arktische Meereis deutlich zurückgegangen. Dieser Eisrückgang wurde durch Satellitenbeobachtungen gut beobachtet. Dagegen haben regionale und globale Klimamodelle immer noch Probleme, den Rückgang entsprechend zu reproduzieren. Sie tendieren dazu, den Meereisrückgang systematisch zu unterschätzen. Die Unterschiede zwischen Modell und Beobachtungen legen nahe, dass die grundlegenden physikalischen Prozesse und Rückkopplungsmechanismen nicht entsprechend in arktischen Klimamodellen repräsentiert werden. Somit sind wahrscheinlich auch die Vorhersagen der Modelle unzureichend. Es ist notwendig, den Ursprung dieser Unstimmigkeit zu identifizieren.

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Ho, Zuleita, Eduard Jorswieck i Sabrina Engelmann. "Information Leakage Neutralization for the Multi-Antenna Non-Regenerative Relay-Assisted Multi-Carrier Interference Channel". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121245.

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In heterogeneous dense networks where spectrum is shared, users' privacy remains one of the major challenges. On a multi-antenna relay-assisted multi-carrier interference channel, each user shares the spectral and spatial resources with all other users. When the receivers are not only interested in their own signals but also in eavesdropping other users' signals, the cross talk on the spectral and spatial channels becomes information leakage. In this paper, we propose a novel secrecy rate enhancing relay strategy that utilizes both spectral and spatial resources, termed as information leakage neutralization. To this end, the relay matrix is chosen such that the effective channel from the transmitter to the colluding eavesdropper is equal to the negative of the effective channel over the relay to the colluding eavesdropper and thus the information leakage to zero. Interestingly, the optimal relay matrix in general is not block-diagonal which encourages users' encoding over the frequency channels. We proposed two information leakage neutralization strategies, namely efficient information leakage neutralization (EFFIN) and local-optimized information leakage neutralization (LOPTIN). EFFIN provides a simple and efficient design of relay processing matrix and precoding matrices at the transmitters in the scenario of limited power and computational resources. LOPTIN, despite its higher complexity, provides a better sum secrecy rate performance by optimizing the relay processing matrix and the precoding matrices jointly. The proposed methods are shown to improve the sum secrecy rates over several state-of-the-art baseline methods.

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Crawford, Cecelia L. "Using a collaborative center for integrative reviews and evidence summaries to narrow the education-practice-research gap". Thesis, Western University of Health Sciences, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3557774.

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The overarching purpose of this dissertation project was to design a collaborative center for integrative reviews and evidence summaries (CCIRES) to advance the state of the art and science of nursing knowledge and narrow the education-practice-research gap. The CCIRES program was created as a web-based platform embedded in the Kaiser Permanente Southern California infrastructure. The specific purpose of this project was to implement CCIRES via that infrastructure, and evaluate the implementation, structures, processes, and usability of CCIRES. The Diffusion of Innovations was the theoretical framework, as supported by the Model of Diffusion in Service Organizations and the Colorado Patient-Centered Interprofessional Evidence-Based Practice Model. These theoretical perspectives and models informed the structures and processes for the design, implementation, and evaluation of the CCIRES innovation. The literature captured the history of the education-practice-research gap and the use of translational research to support evidence-based nursing practice. A rigorous methodology involving formative and summative evaluation structured data collection and analyses. Four expert members of CCIRES comprised the sample targeted for voluntary participation in the SWOT web-based survey and construction of a logic model providing the data outcomes. NVIVO was the qualitative software program chosen for SWOT data storage and management. The SWOT analysis identified nine individual themes, with three themes spanning all categories and four themes populating four separate categories. These data results allowed deep examination of the essential core functions needed to achieve CCIRES' goals and succeed as a program. Group consensus during a webinar meeting was the data analysis technique for the construction of the 2012 CCIRES logic model. CCIRES members analyzed the alignment of multiple model components to understand the gaps, commonalities, and interrelated elements needed for a successful academic-service partnership program. Secondary outcomes included increased membership, website design, increased evidence review competencies, development of resources, and tool testing. CCIRES' goal of narrowing the education-practice-research gap facilitates the delivery of meaningful knowledge into the caring hands of professional nurses. CCIRES next bold step is to partner with other influential groups seeking to increase the breadth, depth, and rigor of the evidence. By heeding this call to action, CCIRES can translate, diffuse, and disseminate 21^st Century nursing knowledge that has meaning for the two people who seek it and need it most—the nurse and the patient.

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39

Zharova, Alona. "Measures of University Research Output". Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18799.

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New Public Management unterstützt Universitäten und Forschungseinrichtungen dabei, in einem stark wettbewerbsorientierten Forschungsumfeld zu bestehen. Entscheidungen unter Unsicherheit, z.B. die Verteilung von Mitteln für den Forschungsbedarf und Forschungszwecke, erfordert von Politik und Hochschulmanagement, die Beziehungen zwischen den Dimensionen der Forschungsleistung und den resultierenden oder eingehenden Zuschüssen zu verstehen. Hierfür ist es wichtig, die Variablen der wissenschaftlichen Wissensproduktion auf der Ebene von Individuen, Forschungsgruppen und Universitäten zu untersuchen. Das Kapitel 2 dieser Arbeit analysiert die Ebene der Individuen. Es verwendet die Beobachtungen der Forscherprofile von Handelsblatt (HB), Research Papers in Economics (RePEc, hier RP) und Google Scholar (GS) als meist verbreitete Ranking-Systeme in BWL und VWL im deutschsprachigen Raum. Das Kapitel 3 liefert eine empirische Evidenz für die Ebene von Forschungsgruppen und verwendet die Daten eines Sonderforschungsbereichs (SFB) zu Finanzinputs und Forschungsoutput von 2005 bis 2016. Das Kapitel beginnt mit der Beschreibung passender Performanzindikatoren, gefolgt von einer innovativen visuellen Datenanalyse. Im Hauptteil des Kapitels untersucht die Arbeit mit Hilfe eines Zeit-Fixed-Effects-Panel- Modells und eines Fixed-Effects-Poisson-Modells den Zusammenhang zwischen finanziellen Inputs und Forschungsoutputs. Das Kapitel 4 beschäftigt sich mit dem Niveau der Universitäten und untersucht die Interdependenzstruktur zwischen Drittmittelausgaben, Publikationen, Zitationen und akademischem Alter mit Hilfe eines PVARX-Modells, einer Impulsantwort und einer Zerlegung der Prognosefehlervarianz. Abschließend befasst sich das Kapitel mit den möglichen Implikationen für Politik und Entscheidungsfindung und schlägt Empfehlungen für das universitäre Forschungsmanagement vor.
New Public Management helps universities and research institutions to perform in a highly competitive research environment. Decision making in the face of uncertainty, for example distribution of funds for research needs and purposes, urges research policy makers and university managers to understand the relationships between the dimensions of research performance and the resulting or incoming grants. Thus, it is important to accurately reflect the variables of scientific knowledge production on the level of individuals, research groups and universities. Chapter 2 of this thesis introduces an analysis on the level of individuals. The data are taken from the three widely-used ranking systems in the economic and business sciences among German-speaking countries: Handelsblatt (HB), Research Papers in Economics (RePEc, here RP) and Google Scholar (GS). It proposes a framework for collating ranking data for comparison purposes. Chapter 3 provides empirical evidence on the level of research groups using data from a Collaborative Research Center (CRC) on financial inputs and research output from 2005 to 2016. First, suitable performance indicators are discussed. Second, main properties of the data are described using visualization techniques. Finally, the time fixed effects panel data model and the fixed effects Poisson model are used to analyze an interdependency between financial inputs and research outputs. Chapter 4 examines the interdependence structure between third-party expenses (TPE), publications, citations and academic age using university data on individual performance in different scientific areas. A panel vector autoregressive model with exogenous variables (PVARX), impulse response functions and a forecast error variance decomposition help to capture the relationships in the system. To summarize, the chapter addresses the possible implications for policy and decision making and proposes recommendations for university research management.

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40

Großmann, Knut. "Tradition und Gegenwart bei der Analyse des thermischen Verhaltens spanender Werkzeugmaschinen: Tagungsband 16. Dresdner Werkzeugmaschinen-Fachseminar, 21. und 22. März 2013 Dresden: Gewidmet dem 100. Geburtstag von Prof. Dr.-Ing. habil. Dr. h.c. Horst Berthold". Technische Universität Dresden, 2013. https://tud.qucosa.de/id/qucosa%3A27057.

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Die Dresdner Werkzeugmaschinen-Fachseminare sind ein Forum zu ausgewählten Spezialthemen der Entwicklung und Nutzung von Werkzeugmaschinen. Das 16. WZM-Fachseminar berichtetet inhaltlich detailliert von aktuellen Arbeiten im Rahmen des DFG-Sonderforschungsbereiches "Thermo-Energetische Gestaltung von Werkzeugmaschinen" (SFB/TR 96) an den Standorten Dresden, Aachen und Chemnitz. Die Fachbeiträge berichten über experimentelle und modellgestützte Analyse von Wärmequellen und -übertragung in spanenden Werkzeugmaschinen sowie zu Lösungsansätzen zur Korrektur und Kompensation der thermo-elastischen Verlagerungen.:H. P. Schossig DMG, Pfronten: Thermik-Forschung und die Umsetzung der Erkenntnisse in Maschinenkonzepten bei DMG K. Großmann Sprecher des DFG-SFB Transregio 96 IWM, TU Dresden: Thermo-Energetische Gestaltung von Werkzeugmaschinen F. Klocke; M. Brockmann WZL, RWTH Aachen, K. Großmann; Ch. Städel IWM, TU Dresden: Untersuchungen des Zerspanungsprozesses hinsichtlich auftretender Wärmeströme und Temperaturen R. Werner; St. Winkler EWA, TU Chemnitz, Ch. Brecher; D. Haber WZL, RWTH Aachen: Verlustleistungen in einer Vorschubachse und die daraus resultierende Temperaturverteilung R. Kneer; S. Vieler WSA, RWTH Aachen, K. Großmann; St. Schroeder IWM, TU Dresden: Messungen des Wärmeübergangs an Fugenkontakten von Werkzeugmaschinen J. Weber; Jul. Weber IFD, TU Dresden, G. Schmidt; U. Semmler Fraunhofer IWU, Chemnitz: Fluidische Kühlung von Motorspindeln und Werkzeugen W.-G. Drossel; St. Ihlenfeldt; C. Zwingenberger Fraunhofer IWU, Chemnitz, K. Großmann; St. Schroeder IWM, TU Dresden: Modellierung des Wärmeaustauschs Maschine-Umgebung A. Voigt; J. Wensch; A. Naumann IWR, TU Dresden: Defektkorrektur bei Mittelungsverfahren in der Zeitintegration des Temperaturverhaltens K. Großmann; A. Galant IWM, TU Dresden, M. Beitelschmidt; M. Partzsch IFKM, TU Dresden: Strukturveränderlichkeit in FEM und Blocksimulation bei der Berechnung von Temperaturfeldern K. Großmann; M. Merx IWM, TU Dresden: Thermografie und Nahbereichs-Fotogrammetrie zur Erfassung von Temperatur- u. Verlagerungsfeldern Ch. Brecher; M. Wennemer WZL, RWTH Aachen: Eigenschaftsmodellbasierter Ansatz zur Korrektur thermo-elastischer Verlagerungen K. Großmann; Ch. Städel IWM, TU Dresden: Simulative Erweiterung der Datenbasis zur korrelativen Korrektur thermo-elastischer Verlagerungen W.-G. Drossel; Ch. Ohsenbrügge Fraunhofer IWU, Chemnitz: Materialeffekte und Funktionsmechanismen zur Wärmefluss-Steuerung

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41

"HAEC News". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-132486.

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"HAEC News". Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A27114.

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"HAEC News". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-120539.

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Li, Hsueh Feng, i 李雪鳳. "The Establishment of a School Library Media Center-A Collaborative Action Research". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/19484170988068815733.

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碩士
國立嘉義大學
國民教育研究所
89
The purpose of this study was to develop and evaluate a school library media center volunteer program. Furthermore, problems occurring in the process of establishment were also examined. The collaborative action research was used as a framework in this study. The researcher and the teacher librarian, who supervised the school library media center program, cooperatively planed a volunteer program and evaluated its effectiveness. At the same time, the methods of interview, observation, document analysis, panel discussion, as well as surveys were also used in this study. The major findings of this research were as follows: 1. Recruitment strategies should be multiple in order to address the needs of volunteers with different backgrounds. The description and timeframe of required duties should be explained clearly in the announcements. 2. The contents of training workshops should be determined by the requirements of the duties and responsibilities. Besides lectures and handouts, chances for practicing what the volunteers have learned in the workshops were also important. The school may invite suitable scholars from nearby communities or colleges to be the speakers. 3. The methods of journal writing, needs-form filling and grouping were some available means for supervising volunteers in the school library media center. However, the day-to-day management and guidance of the work of the volunteers was not feasible in the school. 4. An annual volunteer recognition event was conducted to reward the contribution of volunteers to the school. As for the methods of informal recognition of volunteer service included access to the school conference room, acquiring special certifications and “Thank You’s” cards. In addition, funding, school administrative support, good volunteer coordinator also were the important elements of a successful volunteer program in the school library media center. On the other hand, the results of this study indicated that volunteers could perform some professional tasks except the clerical works in the school. The tasks of instruction, collaborative planning with teachers, interaction with students, and selection of materials were some of them carried out effectively. However, the volunteers should play an assistant role instead of a leading role in these matters. Finally, five suggestions were proposed for the future research.

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"Tradition und Gegenwart bei der Analyse des thermischen Verhaltens spanender Werkzeugmaschinen". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-118570.

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Die Dresdner Werkzeugmaschinen-Fachseminare sind ein Forum zu ausgewählten Spezialthemen der Entwicklung und Nutzung von Werkzeugmaschinen. Das 16. WZM-Fachseminar berichtetet inhaltlich detailliert von aktuellen Arbeiten im Rahmen des DFG-Sonderforschungsbereiches "Thermo-Energetische Gestaltung von Werkzeugmaschinen" (SFB/TR 96) an den Standorten Dresden, Aachen und Chemnitz. Die Fachbeiträge berichten über experimentelle und modellgestützte Analyse von Wärmequellen und -übertragung in spanenden Werkzeugmaschinen sowie zu Lösungsansätzen zur Korrektur und Kompensation der thermo-elastischen Verlagerungen.

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