Spelling suggestions: "subject:"(site)"" "subject:"(sido)""
151 |
Multiple Antenna Broadcast Channels with Random Channel Side InformationShalev Housfater, Alon 11 January 2012 (has links)
The performance of multiple input single output (MISO) broadcast channels is strongly dependent on the availability of channel side
information (CSI) at the transmitter. In many practical systems, CSI may be available to the transmitter only in a corrupted and
incomplete form. It is natural to assume that the flaws in the CSI are random and can be represented by a probability distribution
over the channel. This work is concerned with two key issues concerning MISO broadcast systems with random CSI: performance analysis and system design. First, the impact of noisy channel information on system performance is investigated. A simple model is formulated where the channel is Rayleigh fading, the CSI is corrupted by additive white Gaussian noise and a zero forcing precoder is formed by the noisy CSI. Detailed analysis of the
ergodic rate and outage probability of the system is given. Particular attention is given to system behavior at asymptotically
high SNR. Next, a method to construct precoders in a manner that accounts for the uncertainty in the channel information is
developed. A framework is introduced that allows one to quantify the tradeoff between the risk (due to the CSI randomness) that is
associated with a precoder and the resulting transmission rate. Using ideas from modern portfolio theory, the risk-rate problem is
modified to a tractable mean-variance optimization problem. Thus, we give a method that allows one to efficiently find a good
precoder in the risk-rate sense. The technique is quite general and applies to a wide range of CSI probability distributions.
|
152 |
Techniques of Side Channel CryptanalysisMuir, James January 2001 (has links)
The traditional model of cryptography examines the security of cryptographic primitives as mathematical functions. This approach does not account for the physical side effects of using these primitives in the real world. A more realistic model employs the concept of a <I>side channel</I>. A side channel is a source of information that is inherent to a physical implementation of a primitive. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be detrimental to the security of ciphers like DES and RSA. This thesis surveys the techniques of side channel cryptanalysis presented in [Kocher1996], [Boneh1997], and [Kocher1998] and shows how side channel information can be used to break implementations of DES and RSA. Some specific techniques covered include the timing attack, differential fault analysis, simple power analysis and differential power analysis. Possible defenses against each of these side channel attacks are also discussed.
|
153 |
Distributed Full-duplex via Wireless Side Channels: Bounds and ProtocolsBai, Jingwen 16 September 2013 (has links)
In this thesis, we study a three-node full-duplex network, where the infrastructure node has simultaneous up- and downlink communication in the same frequency band with two half-duplex nodes. In addition to self-interference at the full-duplex infrastructure node, the three-node network has to contend with the inter-node interference between the two half-duplex nodes. The two forms of interferences differ in one important aspect that the self-interference is known at the interfered receiver. Therefore, we propose to leverage a wireless side-channel to manage the inter-node interference. We characterize the impact of inter-node interference on the network achievable rate region with and without a side-channel between the nodes. We present four distributed full-duplex inter-node interference cancellation schemes, which leverage the device-to-device wireless side-channel for improved interference cancellation.
Of the four, bin-and-cancel is asymptotically optimal in high signal-to-noise ratio limit which uses Han-Kobayashi common-private message splitting and achieves within 1 bits/s/Hz of the capacity region for all values of channel parameters. The other three schemes are simpler compared to bin-and-cancel but achieve the near-optimal performance only in certain regimes of channel values. Asymptotic multiplexing gains of all proposed schemes are derived to show analytically that leveraging the side channel can be highly beneficial in increasing the multiplexing gain of the system exactly in those regimes where inter-node interference has the highest impact.
|
154 |
Rear side airbag of the future : And about its purpose to protect the passenger / Framtidens sidoairbag för baksätet : Och om dess syfte att skydda passagerarenGustavsson, Johan, Holmquist, Karin January 2011 (has links)
This project aims to develop a rear side airbag and to investigate how the passenger in the rear seat is in need of protection in a side impact. It was found from the literature study that the head of children and thorax of adults are the most exposed body regions in side impacts. The side collision test done with a barrier by LINCAP (Lateral Impact, New Car Assessment Program) was found to produce the highest force on the rear-seated dummy, in comparison to the same test by IIHS (Insurance Institute Highway Safety), and that a high combined pelvic force results in a lower rating of the vehicle. The objective of the airbag concepts is to offer protection area to the most exposed body regions. The airbags are designed with the presumption that the occupant uses a seat belt and a pretensioner to limit the forward motion of the body, with the rationale that this enables design of airbags with reasonable manufacturing costs. The three new concepts of airbags were: thorax; thorax/pelvis and thorax/pelvis extended. From sled tests with the three new airbag concepts, it was found that an airbag, compared to no airbag, reduces the risk of injury at thorax by 70 percentage units and the force on pelvis is considerably reduced in a side impact. The thorax bag showed a reduction of the rib deflection compared to no airbag, but a high force on the pelvis motivates a protection area of pelvis. The tests with the two larger bags thorax/pelvis and thorax/pelvis extended resulted in a better protection of thorax, abdomen and pelvis than without airbag. Problems with positioning the pelvis area of the bags was noticed but not solved and may be a task in further investigations.
|
155 |
Pretreaments of Chinese Agricultural residues to increase biogas productionWang, Yu January 2010 (has links)
Development of biological conversion of lignocellulosic biomass to biogas is one approach to utilize straw comprehensively. However, high lignin contents of lignocellulosic materials results in low degradation. The main aim of this study was to investigate the appropriate pre-treatment to increase biogas production from Chinese agricultural residues. In this study, Chinese corn stalk, rice plant and wheat straw were evaluated as substrates by applying three different pre-treatments. The investigated pre-treatment were mechanical pre-treatment (cut whole straw into 1-1.5cm) combination of thermal and alkali pre-treatment (1M/L NAOH, 80℃,15 hours) and biological pre-treatment(enzymes provided by Scandinavian Biogas Fuels AB). Biogas production of these substrates was evaluated by batch digester; Sewage sludge from Nykvarn treatment plant and current digesters (Scandinavian Biogas Fuels AB )was the co-digestive substrate which seeded in batch with straw of all pre-treatments. The results indicate that at least 50% of organic contents in Chinese agricultural residues could be converted to biogas by these pre-treatments. The optimizing biogas yield is achieved from Chinese corn stalk with combination of thermal and alkali pre-treatment, Chinese rice plant and wheat straw from pre-hydrolysis pre-treatment respectively .Chinese wheat straw has the most biogas potential from combination of thermal and alkali pre-treatment.
|
156 |
Techniques of Side Channel CryptanalysisMuir, James January 2001 (has links)
The traditional model of cryptography examines the security of cryptographic primitives as mathematical functions. This approach does not account for the physical side effects of using these primitives in the real world. A more realistic model employs the concept of a <I>side channel</I>. A side channel is a source of information that is inherent to a physical implementation of a primitive. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be detrimental to the security of ciphers like DES and RSA. This thesis surveys the techniques of side channel cryptanalysis presented in [Kocher1996], [Boneh1997], and [Kocher1998] and shows how side channel information can be used to break implementations of DES and RSA. Some specific techniques covered include the timing attack, differential fault analysis, simple power analysis and differential power analysis. Possible defenses against each of these side channel attacks are also discussed.
|
157 |
Patientens tillfredställelse med information om medicinering och dess biverkningarMostamand, Alexander, Engström, Joachim January 2011 (has links)
SAMMANFATTNING Syfte: Syftet med denna studie var att på ett sjukhus i Mellansverige undersöka hur tillfredställda patienterna var med information om läkemedelsbiverkningar Syftet var även att undersöka grad av oro över eventuella biverkningar och jämföra om det fanns någon könskillnad gällande detta. Metod: Studiens design var en kvantitativ tvärsnittsstudie med deskriptiv och jämförande statistik. Data samlades in genom en Studiespecifik enkät. Antalet svarande var 29 inneliggande patienter under 10 veckor som uppfyllde inklusionskriterierna. Resultat: Resultatet visade att hälften av deltagarna inte hade fått information om läkemedelsbiverkningar och att 78 % uppgav sig vilja ha mer information. Nio av tio deltagare instämde till att vara oroliga över eventuella biverkningar och 64 % uppgav att de var osäkra eller inte visste vart de skulle vända sig vid frågor om biverkningar. Trots detta var drygt hälften av deltagarna delvis eller helt nöjda med den information de fått. Ingen statistik signifikant könsskillnad kunde påvisas i grad av oro. Slutsats: Resultatet visar att mer och tydligare information bör ges till patienterna om eventuella läkemedelsbiverkningar. Vidare forskning är nödvändigt då mätningen av tillfredställelse ger ett motsägelsefullt resultat. / ABSTRACT Aim: The aim of this study was to investigate how satisfied patients where with information about medical side effects in a hospital in central Sweden. The aim was also to investigate the level of worry for any side effects and compare the level of worry between genders. Method: The design of the study was quantitative, cross-sectional. Data were collected through a study specific questionnaire. Respondents were 29 hospitalized patients who met the inclusion criteria during a 10 week period. Findings: The results showed that half of the participants had not received information about medical side effects and that 78% claimed they wanted more information. Nine out of ten participants agreed with being concerned about possible medical side effects and 64% said they were unsure or did not know where to turn with questions about side effects. Despite this, over half of the participants were partially or completely satisfied with the information they had received. No difference was detected in the level of worry between genders. Conclusion: The results show that more information and more distinct information should be given to patients about possible medical side effects. Further research is necessary since the measuring of satisfaction gives a contradictory result
|
158 |
Study of double-sided ZnO piezoelectric transducerChu, Yu-hsien 15 August 2011 (has links)
This investigation examines a novel means of integrating high-performance ZnO piezoelectric thin films with a flexible stainless steel substrate (SUS304) to fabricate a double-sided piezoelectric transducer. The double-sided piezoelectric transducer is constructed by depositing ZnO piezoelectric thin films on both the front and the back sides of SUS304 substrate. The titanium (Ti) and platinum (Pt) layers were deposited using a dual-gun DC sputtering system between the ZnO piezoelectric thin film and the back side of the SUS304 substrate. Scanning electron microscopy and X-ray diffraction of ZnO piezoelectric films reveal a rigid surface structure and highly c-axis-preferring orientation. To fabricate a transducer with a resonant frequency of about 80 Hz, a cantilever length of 1 cm and a vibration area of 1 cm2 are designed, based on the cantilever vibration theory. The maximum open circuit voltage of the power transducer is approximately 18 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.3 £gW/cm2 is obtained from the transducers with a load resistance of 6 M£[.
|
159 |
Displacement Mechanism of Concrete Artificial ReefsLi, Yi-Lun 07 September 2011 (has links)
The purpose of this study was to integrate the principles of marine geotechnical engineering, underwater acoustic and optical observation techniques into studying the distribution of seafloor sediments and engineering stability of artificial reefs off Yong-an Harbor, Kaohsiung County, south-western coast of Taiwan. The artificial reefs were deployed to the testing site in November 9th, 1996. The goal of this study was intended to describe the engineering status of this reef site and to investigate whether these reefs were moved and buried or not; as well as, to predict whether additional reefs should be deployed to this site in the future.
Long-term monitoring of underwater targets was conducted by using of side-scan sonar system, echo sounder, sub-bottom profiler, and underwater video camera. The utility of side-scan sonar system was to depict the topography and terrain features of the seabed. The other equipments were used to complement and cross correlate the results of side-scan sonar observations. In this study, wave forces against reef were estimated by Morison¡¦s equation(ex. Huang, 1995), scouring depth was calculated by Silvester¡¦s experience equation (Silvester, 1974), and the settlement of reefs by theoretical consolidation equation(ex. Das, 1990).
The topography of Yung-an reef site is generally gentle and monotonous. The major texture of surficial sediments in this site was sandy silt, and some gravel was distributed at the southern part of the site.
In terms of the stability on the artificial reefs project, Typhoon was the main factor which causes the reef to slide or roll. Verified by theoretical analysis and monitoring, the study area of the original stacked reefs has tumbled during the research period, while the remaining non-stacked reef shows insignificant displacement and quantity of the settlement found no cases being buried.
To sum up, Yong-an artificial reef district in Kaohsiung county, respectively as A, B, C; the stacked reef under normal condition has found no significant reef being buried and moving traces and artificial reefs can fully elaborate by the gathers of the fish. According to the viewpoint of this project , "Direct contact with the reef and the body of the sea-bed " both the forces of the waves and ocean currents when a typhoon strikes is not easy for the reefs to glide. The "stacked reef" which causes the reef to slide or roll when typhoon occurs was caused by both the forces of the waves and ocean currents.
"Direct contact with the reef and the body of the sea-bed " in the case of wave period of 10 sec, analysis shows that the wave height must be greater than 5.8 m in order to make the reef slide. "Stacked reef" in the case of wave period of 10 sec, analysis shows that the wave height must be greater than 4.5 m in order to make the reef roll.
|
160 |
Research on Searching and Positioning of Buried Underwater PipelinesHsiao, Po-yuan 03 February 2005 (has links)
In recent years, ocean has become a place to dispose of industrial and civil waste waters. Hence, there are more and more projects to establish offshore outflow pipes. These underwater pipes should be kept monitored in order to maintain their functions specifically. The purpose of this research was to explore the two outflow pipes in Kaohsiung offshore area, i.e., Chung-chou outflow pipe and Tso-ying outflow pipe, by using an integrated surveying system which includes a side-scan sonar and a sub-bottom profiler. The ultimate objective was to investigate the feasibility of this system in searching and positioning of buried underwater pipelines.
Based on this investigation, the offshore section of Chung-chou outflow pipe is about 2.8km in length and extends offshore to the direction of 38o from the west to the south. The water depth at the end of this pipe is about 21m. Among the 2.24km section initiated at the offshore end of the pipe, the buried depths are between 2.2m and 3.2m. There are two disposed gravel zones around the offshore end of the pipe. The first zone is about 130m in length and 10m wide. The second zone is 220m in length and 20m wide. Moreover, based on the side scan sonar images, there are 71 protective concrete blocks located around Chung-chou outflow pipe. The offshore section of Tsao-ying outflow pipe is about 4.76 km in length and extends to the direction of 20o from the west to the south. The water depth at the end of this pipe is about 17m. Among the 3.7km section initiated at the offshore end of the pipe, the buried depths are about 1.0 to 2.5m. A disposed gravel zone with dimensions of 330m in length and 10m wide is located at the end of this pipe. In addition, there are 43 protective blocks located around this outflow pipe.
This investigation, incorporated the results conducted on the other three underwater outflow pipes(i.e., Chishui creek outflow pipe, Chinese Petroleum Corporation underwater petroleum pipe off Kaohsiung Harbor and Liuchiuyu water transport pipe), concluded that as far as the buried underwater pipes that are thicker than 1m in diameter are concerned, the integrated system of side scan sonar and sub-bottom profiler provides an useful and trustful tool to get the locations and the buried depth of outflow pipes, as well as the distribution of the protective concrete blocks around these pipes. As to the pipes that are less than 20cm in diameter, the pipes can¡¦t be detected by this equipment. For the pipes that are between 20cm and 1m in diameter, due to limited information collected up to this moment, extensive investigation need to be conducted until a clear understanding can be deduced.
|
Page generated in 0.0356 seconds