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This study evaluates the effect of vibration on adaptation of bulk-fill composite resin. A scanning laser doppler vibrometer measured the frequency and amplitude of a vibratory device (COMO) used for resin placement and visualized its effect on the resin according to depth. FB was placed in simulated cavities (4 mm diameter, 4 mm depth) by different layering methods (incremental filling with two 2-mm-thick layers vs. bulk filling with a single 4-mm-thick layer). The groups were further divided based on the application of vibration during restoration (no vibration vs. vibration). The voids that formed at the bottom surface of the cavity and the bottom, middle, top third, and overall void volumes were measured using micro-computed tomography. The frequency and amplitude of the COMO were approximately 149 Hz and between 26 and 51 um, respectively. Vibration provided improved surface adaptation and lower void volumes during incremental filling (p < 0.05). Vibration applied with a 4-mm-thick bulk fill had no effect on the adaptation of composite resin (p > 0.05). Void volume was markedly higher in the bottom part in all groups. Application of vibration to the resin with a 2-mm incremental-layering technique produced the best adaptation of the composite resin.

A content analysis was conducted based on the presidential images presented by the leading newspapers and the official presidential office websites in the United States and Korea. Findings reveal d...

Using a Web-based survey targeting visual professionals, this study examines their professional role conceptions along with their views on emerging visual citizen contributors’ roles. While participants’ ratings of the two groups’ roles were generally correlated within each group, no correlations resulted between the two groups with the exception of the civic roles. Further, visual professionals rated their roles as significantly more important for all five roles. When assessing views on citizen-contributed visuals, it was clear that participants evaluated them with a critical eye, expressing dislike toward citizens’ visual contributions and deeming them a threat to their livelihood.

A graphene mesh with arrays of micro-holes was fabricated on a polymer substrate using photolithography for use as an electrode in flexible devices. The optimal mesh structure with high optical transmittance and electrical conductivity was designed using a finite element method, in which the conductivity of the mesh was simulated as a function of structure, size, and periodicity of the hole array. The sheet resistance of the graphene mesh was lowered to that of a graphene monolayer by chemical doping and found to be 330 Ω Sq−1 at 98.5% transparency. The figure of merit of the doped graphene mesh was calculated to be 106 at 98% transmittance, a value that has not yet been reported for any conventional transparent electrode material. Due to strong bonding between the polymer and substrate, the hybrid electrode composed of a silver nanowire (AgNW)/graphene mesh coated with an over-coating layer exhibited more stable electrical characteristics during mechanical fatigue deformation compared to a hybrid film composed of a AgNW/graphene sheet. The AgNW/graphene sheet underwent breakdown at less than 20 000 cycles in cyclic bending tests with 6.5% strain, but the AgNW/graphene mesh showed a 38% increase in resistance at 20 000 cycles and no breakdown even at 100 000 cycles. Therefore, in this study, we propose a hybrid structure composed of a AgNW/graphene mesh, which is optically and mechanically superior to AgNW/graphene sheets, and therefore suitable for application as a transparent electrode in foldable devices with long-term stability.

High data rate at high mobile speed will still be an essential requirement for the future 5G mobile cellular system. High frequency bands above 6 GHz are particularly promising for the 5G system because of large signal bandwidths such high frequencies can offer. By using high gain beamforming antennas, the problem of high propagation loss at high frequencies can be overcome. However, the use of beamforming antennas at such high frequencies requires a significant change in the design of a cellular system. In particular, it requires a significant change in key functions such as cell search, random access, measurement of beams for fast beam adaptation, and various physical control and data channels. In this paper, we propose a new radio frame structure for the future mobile cellular communications system at millimeter wave frequency that addresses such challenges. A testbed was built at Samsung Electronics, Korea, based on the proposed frame structure at 28 GHz with bandwidth of 800 MHz. It attained the downlink (DL) data rate of 7.5 Gbps by delivering four streams of 64 QAM data with code rate of 3/4 to two mobile stations (MSs) located in a close distance to the base station antennas at fixed positions. It also achieved the DL data rate of 1.2 Gbps by delivering single stream of 16 QAM data with code rate of 3/4 to an MS moving at 110 km/h in a single cell of up to 800 m in a line-of-sight environment. Finally, it implemented handover and achieved an average handover interruption time of 21 ms in a three-cell environment, and demonstrated feasibility of mobile cellular communications at millimeter wave frequency.

Twitter has emerged as a popular source of sharing and delivering news information. In tweet messages, URLs to web resources and hashtags are often included. This study investigates the potential of the hyperlinks and hashtags as topical clues and indicators to tweet messages. For this study, we crawled and analyzed about 1.5 million tweets for a 3-month period covering any topic or subject. The findings of this study revealed a power law relationship for the ranking and frequency of a the host names of URLs, and b a pair of hashtags and URLs that appeared in the tweet messages. This study also discovered that the most popular URLs used in tweets come from news and media websites, and a majority of the hyperlinked resources are news web pages. One implication of this study is that Twitter users are becoming more active in sharing already published information than producing new information. Finally, our investigation on hashtags for web resource indexing reveals that hashtags have the potential to be used as indexing terms for co-occurring URLs in the same tweet. We also discuss the implications of this study for web resource recommendation.

The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

An underwater 137Cs (662 keV) and 131I (364 keV) radioisotopes monitoring system has been developed using a 3'' × 3'' NaI(Tl) detector. To estimate the minimum detectable activity and Bq/L conversion factor, an experiment was first conducted with 68Ga (511 keV) in a water tank. For energy spectrum comparison, Monte Carlo simulations were performed for 68Ga, 137Cs, and 131I to determine the conversion factor. The minimum detectable 137Cs and 131I activities for the system are 0.77 and 0.89 Bq/L, respectively.

This study explores the ethical dilemma photojournalists face when professional duty conflicts with the normative ethics of the reading public. The study investigates the public's and photojournalists' perceptions of appropriate reactions to the circumstances surrounding Kevin Carter's Pulitzer Prize-winning photograph of a collapsed Sudanese girl as a vulture awaits her death. The study used an online survey to measure the perceptions of appropriate reactions. Both readers and journalists respondents perceived Carter's photograph of a Sudanese girl suffering from starvation as an accurate documentation of an important social issue. Furthermore, most agreed that the picture was newsworthy and accepted the professional journalistic ethical rationale for making the photograph. The majority indicated that they would have made the photo themselves under similar circumstances, but the readers said that would have done more to help the girl than Carter did.

This study employed a content analysis to examine the visual coverage of the September 11th attacks through images submitted to Pictures of the Year International. This study classified the 667 images into four main themes: events, aftermath, firefighters, and the Muslim world. In an attempt to determine how the September 11th terrorists' attack was framed by photojournalists, this study revealed that most of the images framed strong pro-American perspectives by showing a challenged America and a nation united through patriotism while only limited images introduced different anti-American perspectives.

A web-based survey of administrators (N = 59) and visual instructors (N = 60) was employed to examine the state of visual communication curricula among U.S. journalism and mass communication programs. Findings indicate courses were small, skills-based, and required for a limited number of students. Instructors had strong professional backgrounds, had strong opinions for expanding visual communication education, and had less confidence than administrators did that their students would have competence upon landing a job.

Photojournalists occasionally have to choose between acting as dispassionate observers or becoming Good Samaritans. This study asked photojournalists to assess scenarios of a photojournalist's decision to take a picture of a person suffering severe trauma instead of helping.

HTS (high temperature superconducting) motor that utilizes superconductor as the field winding has advantage of compactness, light weight and high efficiency, but it has an inherent disadvantage that the rotor must be cooled down at cryogenic temperature. Conventionally, HTS rotor was cooled by circulation of cryogenic fluid such as helium or neon, and the cooling system was installed outside of the motor to prevent it from being rotated. In this paper, however, the prototype of the HTS motor with an on-board cryocooler, is fabricated and tested. The experimental system is composed of the stator with conventional copper winding, the rotor with superconductor, and the rotating cryocooler as a novel concept of cooling system. The rotor is fabricated as the race-track coil with 2G, YBCO tape and situated in the 110 mm diameter cryostat. It is designed to minimize heat invasion from room temperature environment and be compatible with the coaxial structure of the cryocooler. The cryocooler is in physically and thermally contact with the HTS rotor while being rotated together. Two kinds of refrigerator, a Stirling refrigerator and an inline-type PTR (Pulse Tube Refrigerator) are used individually as the on-board cryocooler. The whole system is carefully integrated and fabricated for rotating stability. Several temperature sensors and voltage taps are installed to monitor the conditions of the HTS rotor and the cryocooler while their signals are acquired by the bluetooth data acquisition system during the operation. The HTS motor is successfully operated with 120 rpm of rotating speed. In the rotating test, 70 A current is supplied to the superconducting rotor. Further developmental design issues for on-board cryocooling system are addressed and discussed in this paper.

AIM The aim of this biomechanical study was to assess the influence of self-tapping blades in terms of primary implant stability between implants with self-tapping blades and implants without self-tapping blades using five different analytic methods, especially in medium-density bone. MATERIALS AND METHODS Two different types of dental implants (4 × 10 mm) were tested: self-tapping and non-self-tapping. The fixture design including thread profiles was exactly the same between the two groups; the only difference was the presence of cutting blades on one half of the apical portion of the implant body. Solid rigid polyurethane blocks with corresponding densities were selected to simulate medium-density bone. Five mechanical assessments (insertion torque, resonance frequency analysis [RFA], reverse torque, pull-out and push in test) were performed for primary stability. RESULTS Implants without self-tapping blades showed significantly higher values (P 0.05). CONCLUSIONS The outcomes of the present study indicate that the implant body design without self-tapping blades has a good primary stability compared with that with self-tapping blades in medium-density bone. Considering the RFA, a distinct layer of cortical bone on marginal bone will yield implant stability quotient values similar to those in medium-bone density when implants have the same diameter.

When documenting human tragedy, photojournalists frequently face ethical dilemmas in choosing between acting as dispassionate observers and “Good Samaritans.” This study asked whether readers adopt a situational ethics rationale when they assess the photojournalist's decision to make a photograph of a person suffering severe trauma. Using a mixed experimental research design, the study presented a news situation, i.e., a photograph in which a woman was on fire, in differing versions. Results based on the responses of seventy-two readers clearly showed that readers adopted a situational ethics rationale.

The aim of this study was to evaluate the change of marginal bone level radiographically around three different implant systems after 3 years in function. Fifty-four patients were included and randomly assigned to three treatment groups of rough-surface implants (TiUnite, n = 37), hybrid of smooth and rough-surface implants (Restore, n = 38) and rough surface with microthread implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline), 1 and 3 years after loading. A three-level mixed-effect analysis of covariance (ancova) was used to test the significance of the mean marginal bone change of the three implant groups. A total 120 of 135 implants completed the study. None of the implants failed to integrate. Significant differences were noted in the marginal bone loss recorded for the three groups (P < 0.0001). At 3 years, the rough surface with microthread implants had a mean crestal bone loss of 0.59 +/- 0.30 mm; the rough-surface implants, 0.95 +/- 0.27 mm; and the hybrid surface implants, 1.05 +/- 0.34 mm. Within the limitations of this study, rough-surface implants with microthread at the coronal part might have a long-term positive effect in maintaining the marginal bone level against functional loading in comparison with implants without these two features.

We propose a new broadcast strategy for a multiple-input multiple-output (MIMO) system with N transmit antennas at the transmitter and M≤N single antenna receivers. The proposed method, based on dirty-paper coding (DPC), spatially separates the M users but does not suffer from the power loss of classical spatial division multiple access (SDMA). For the special case of M=N=2 and when the two single antenna receivers are assumed to be co-located, the proposed scheme produces a 2 transmit, 2 receiver antenna MIMO transmission system that doubles the symbol rate of MIMO space-time block code (STBC) systems from one to two symbol per transmission time. It is proved theoretically and experimentally that the proposed scheme provides the same performance level as that of MIMO STBC systems (i. e., the Alamouti scheme) for the first symbol, and the same performance as the Bell labs layered space-time (BLAST) system for the second symbol. When compared to the BLAST system, the proposed scheme has the same symbol rate, but achieves significantly better performance, since it provides 2 level diversity per symbol on the first symbol while the BLAST system does not provide any diversity.

Results of a comparative visual analysis of front-page photographs in U.S. newspapers and photographs distributed by the Associated Press and Reuters wire services revealed that gatekeeping decisions played an influential role in the coverage of Hurricane Katrina in the late summer of 2005. Front-page photographs differed significantly from photographs provided by news wires. Overall, our analyses challenge the notion that decisions made by wire services dictate the visual coverage of a news event and suggest that gatekeeping selections and use of available information are key factors in visual framing.

The paper proposes a new duplexing scheme, which is called the hybrid division duplex (HDD), that is suitable for fourth-generation mobile communication systems. The proposed mobile communication system is much more flexible and efficient in providing asymmetric data service and managing intercell interference by exploiting the advantages of both time division duplex (TDD) and frequency division duplex (FDD) schemes. The HDD scheme has a pair of frequency bands such as the FDD, performing a TDD operation using one of the bands in such a manner that allows for simultaneous FDD and TDD operations. Considering the properties of the HDD system architecture, frequency hopping orthogonal frequency division multiple (OFDM) access is adopted in one band for the TDD operation and code division multiple access (CDMA) in the other band for the FDD uplink operation. The important advantage of the HDD scheme is the robustness against cross time slot interference that is inherent to the TDD system, which is caused by the asynchronous downlink/uplink switching boundaries among all neighbor cells. From the simulation results, the proposed system can achieve approximately 7% and 30% improvement with regard to the downlink and uplink throughput, respectively, as compared to the conventional TDD system under cell-independent downlink/uplink traffic asymmetries. It demonstrates that the HDD scheme is a viable solution for future communication systems that are projected to have a cell-independent asymmetric-traffic-supported hierarchical cell structure.

We have demonstrated a broadband radio-over-fiber communication system transmitting wireless signals at the millimeter-wave bands. The system incorporated 25 km of an optical intermediate frequency feeder. 60 GHz orthogonal frequency division multiplexing (OFDM) signal transmission at 155 Mbps with a bit error rate (BER) of less than 10/sup -6/ was achieved within the system cell of a radius of 2.6 m under the channel condition of line-of-sight with choke horn antennas. SNR enhancement of 6 dB for a BER level of 10/sup -6/ was achieved with the forward error correction code, simultaneous synchronization, and channel estimation algorithm.

A random beamforming technique for multiple-input multiple-output (MIMO) systems that simultaneously obtains downlink multiuser diversity gain, spatial multiplexing gain and array gain by feeding back only effective signal-to-noise ratios (SNRs) is described. In addition, power control using waterfilling is employed to improve the throughput of our method in correlated channels. In a slow fading channel, we prove that the throughput of the proposed method converges to that of eigen beamforming when many users are in a cell. The number of users required to achieve capacity bound increases with the number of antennas and SNR was determined. However, the capacity bound is achieved even with a small number of users, e.g., 16 users in a cell, when the SNR is low, e.g., 0 dB, and the number of transmit and receive antenna is small, e.g., two. We also find that the effect of waterfilling is more noticeable in correlated channels.

This article introduces the vision and requirements for future development of mobile communications systems, and discusses several key enabling technologies such as modulation and multiple access schemes, multiple antenna techniques, and an IP-based network, considered important to realize this vision in real-world systems.

For the fast fading channels, e.g., fast mobile channels, non-coherent detection scheme is promising because the receiver does not require to measure the channel information, which results in reducing transmission overhead. In this paper, we compare the bit error rate of two non-coherent encoding/decoding schemes for multiple transmit antennas under fast fading environments when the number of antenna varies from two to three. The first approach is a unitary space-time modulation (USTM) that aims to achieve the non-coherent channel capacity. The second one is a differential space-time block code (DSTBC), which projects information symbols to a number of orthogonal bases that consist of the previously sent symbols. We exhibit the fact that the block length of both schemes affects the performance significantly rather than encoding/decoding methods when the channel varies fast. In addition, we present some problems of the DSTBC sending the complex symbols with more than two transmit antennas.

Statement of Problem. The mechanics of implant screw loosening or fracture are well understood in the field of engineering. They have not been as widely explored in dentistry. Purpose. This study investigated the effects of simulated mastication on implant components and used wave analysis to document the basic mechanisms of screw loosening in a simulated oral environment. Material and Methods. A pneumatic cylindrical cyclic loading device was fabricated to simulate masticatory movement. Thirteen standard abutments were connected on external hexagonal implants with titanium abutment screws tightened to 20 Newton centimeters (Ncm), and single crowns were retained with gold screws tightened to 10 Ncm on each abutment, respectively. Ten single-implant crowns were loaded with the use of a cyclic loading device with 100 N of force at 30° angles to the long-axis for 0.2 seconds of contact time with a frequency of 1 Hz. Three crowns were loaded vertically under the same conditions to serve as the control group. The effects of up to 1 million cyclic loads and various tightening torque forces (2, 4, 6, 8, 10, and 12 Ncm) on screw loosening were evaluated by wave analysis. A software program was written to record every wave mode and to stop the machine automatically if the amount of horizontal displacement of the crown was more than 0.5 mm, which was designated to represent perceptible loosened implant crown mobility clinically. The general wave patterns and characteristics of loosened and stable screws and the effect of various tightening torques were analyzed by comparing the differences in wave patterns. Results. The wave mode was divided into 4 stages for loosened gold screws: initial displacement, initial vibration, elastic deformation, and recovery stage. However, the initial displacement and initial vibration stages were not discernible for stable gold screws. Of the 10 gold occlusal screws, 4 loosened before the 1 million cyclic loads in the 10 single crowns tested. There was no screw loosening in the control group. There was no effect of screw loosening on the elastic deformation stage. Conclusion. Within the limitations of this study, tightening torque had a significant effect on screw loosening. It would appear that more than 10 Ncm of tightening torque should be recommended for the gold screws in this external hexagon implant system. (J Prosthet Dent 2002;88:402-8.)

In this paper, we report a preliminary study on the electrical and optical properties of the first P-on-N SiPM prototype developed at KAIST with a collaboration of NNFC. The sensors were fabricated on a 200 mm n-type silicon epitaxial-layer wafer via customized CMOS process at NNFC. Measurements on the reverse current were carried out on a wafer-level with an auto-probing station and breakdown voltage was found as 32.3 V. As for optical characterization, gain, dark count rate, and photon detection efficiency have been measured as a function of bias voltage at room temperature. In particular, we show that the device had a comparable gain of ~ 106 with respect to conventional PMTs and had a peak sensitivity in blue light regime. Furthermore, we attempt to explain possible causes of some of phenomena seen from the device characterization.

A new nonlinear equalizer for high-density magnetic recording channels is presented. It has a structure of the decision-feedback equalizer (DFE) with a nonlinear model at the feedback section and a dynamic threshold detector. The feedback nonlinear model is a sequence of look-up tables (LUTs) indexed by time, and each table is addressed by a transition pattern formed by one future and /spl nu/ past transitions. We call this new nonlinear equalizer the pattern-dependent DFE (PDFE). The feedback nonlinear model cancels the trailing nonlinear intersymbol interference (ISI), and then the data decision is made by considering the precursor nonlinear ISI caused by one future symbol. We propose a tap optimization criterion SNR/sub d/ for the PDFE which in effect tries to maximize the output signal to noise ratio, and derive a closed-form solution for the tap values. We compare the detection performance of PDFE with that of the DFE and the RAM-DFE on experimental channels. The RAM-DFE is a DFE with one large LUT at its feedback section. The results show that the PDFE yields a significant performance improvement over the DFE and the RAM-DFE. Also the PDFE derived in this paper achieves a superior performance compared with the PDFE derived by the minimum mean-square-error criterion.

A Silicon Photo Multiplier (SiPM) is states of arts radiation detector, it is alternative to PM-Tube. But, availability research of SiPM is not entirely satisfactory. In this study, we suggest the radiation detector module coupled with the SiPM and the plastic scintillator, and then, evaluate the availability of detector module for Cs-137 dosimetry.

In wafer-scale CMOS image sensors, the 3-transistor structure suffers from its low speed. To overcome this limitation, we propose a digital pixel sensor which has a digital-pixel output instead of analog-pixel output as in a conventional 3-transistor pixel. The digital pixel sensor can provide a high frame because it eliminates analog-to-digital conversion time. In addition, it removes the noise from long analog-signal paths. As a prototype, we designed a 4.5mm × 4.0mm chip having 24 × 16 pixels of 100µm × 100µm using standard 0.18µm CMOS technology. With 2MHz clock, the readout time for each pixel was 6micro seconds. When 3000pixels are in each column of a full-wafer-size CMOS image sensor, 50fps can be achieved with the digital pixels based on pulse width modulation.

This paper presents a circuit of a digitized position decoder circuit for brain PET consisting of Silicon Photomultiplier (SiPM). Difference of proposed circuit and traditional circuit is the existence of analog-to-digital convertor (ADC). In this work, we conclude that the combination of ADC, field programmable gate array (FPGA) and digital data acquisition (DAQ) board can be substitute for an existing analog DAQ.

The aim of this biomechanical study was to assess the influence of self-tapping blades in terms of primary implant stability between implants with self-tapping blades and implants without self-tapping blades using five different analytic methods, especially in medium-density bone.Two different types of dental implants (4 × 10 mm) were tested: self-tapping and non-self-tapping. The fixture design including thread profiles was exactly the same between the two groups; the only difference was the presence of cutting blades on one half of the apical portion of the implant body. Solid rigid polyurethane blocks with corresponding densities were selected to simulate medium-density bone. Five mechanical assessments (insertion torque, resonance frequency analysis [RFA], reverse torque, pull-out and push in test) were performed for primary stability.Implants without self-tapping blades showed significantly higher values (P0.001) in four biomechanical assessments, except RFA (P=0.684). However, a statistically significant correlation could not be detected between insertion torque values with the four different outcome variables (P0.05).The outcomes of the present study indicate that the implant body design without self-tapping blades has a good primary stability compared with that with self-tapping blades in medium-density bone. Considering the RFA, a distinct layer of cortical bone on marginal bone will yield implant stability quotient values similar to those in medium-bone density when implants have the same diameter.

According to the commons model of cognitive radio, the activity of secondary (unlicensed) nodes is required to guarantee quality-of-service (QoS) constraints on the transmission of primary (licensed) terminals. Towards this goal, vertical handover between different radio interfaces is currently being investigated as a promising solution to enhance flexibility in unlicensed channel access. In this paper, we propose an analysis of cognitive radio with vertical handover capability in a simple scenario with one secondary node and two primary nodes that employ different radio interfaces with packet-based transmission. The maximum stable throughput of the secondary node is evaluated under maximum-delay QoS constraints on the primary activity as a function of system geometry, QoS constraints and sensing errors. Numerical results show the relevant advantages of optimal vertical handover in terms of the throughput of secondary nodes.

In this paper, a cognitive radio scenario composed of one primary (licensed) node and M secondary (unlicensed) nodes coexisting in the same spectral resource is considered. According to the commons model of cognitive radio, the secondary nodes are required to guarantee quality-of-service (QoS) constraints on the primary activity. Assuming a collision channel model, the stability region of the arrival rates at the secondary queues is investigated for given primary throughput and QoS constraints defined in terms of average delay of primary packets. Inner and outer bounds on the stability region are derived. The analysis is carried out at first for the case M = 2 and then generalized for any number of secondary nodes (M > 2), and is based on the concept of dominant systems. The results shed light on the impact of detection errors at the secondary nodes and of different levels of QoS requirements of the primary user to the achievable (stability) rate region of the secondary nodes. Numerical results suggest that the derived inner bound is a tight approximation of the real stability region.

Antenna selection strategies for multiple-input multiple-output (MIMO) wireless systems is presented. In our scheme, both transmit and receive antenna selection is done at the receiver, significantly reducing feedback information to the transmitter. Row/column probability density function (pdf) is used for antenna selection to reduce computational complexity without performance degradation. Unlike other schemes, we used two different antenna selection algorithms both for high SNR and low SNR regime, achieving additional performance gain in comparison with the single antenna selection algorithm. Simulation results show that our scheme nearly approaches to the optimal closed-loop capacity (known as water-filling capacity).

We present a multiple-input multiple-output (MIMO) relay system with hybrid automatic repeat request (HARQ) protocols which can achieve better outage behaviors than simple MIMO cooperative diversity schemes. Using repetition based and Alamouti based HARQ scheme, we can achieve better diversity gains without increasing additional transmit power. This system can be a practical solution for a new system which requires lower deployment costs and limited power in each nodes.

In this paper, first, it has been discussed hot carrier reliability in both Pch, RCAT and SRCAT. Second, we showed the origin of electric field suppression where the supply-voltage is applied at the same bias condition. Furthermore, we discuss the effects of ion implant process

In this paper, we propose a recursive space time decoding method for orthogonal frequency division multiplexing (OFDM) systems exploiting multiple transmit antenna diversity when the channels are fast fading. We first develop a computationally efficient space-time decoding method involving a matrix inversion to mitigate the channel variation effect. We then further reduce the computational complexity of the matrix inversion decoding method via a recursive formulation. Computer simulation results show that the proposed recursive decoding has much better BER performance than Alamouti decoding, requiring much less computation than the matrix inversion decoding. Moreover, the relative advantage in BER performance of the proposed scheme over Alamouti decoding stands out as the Doppler frequency increases

In this paper, we construct a differential spatial multiplexing method that can trade-off spatial diversity for increased transmission rate in differential multi-input multi-output (MIMO) systems. To achieve a desired multiplexing gain while providing simple encoding and decoding, Gram-Schmidt algorithm is used at the transmitter to construct the unitary transmission matrix. In addition, by applying optimum scaling factors to generate transmission matrix, the symbol error rates can be minimized. Because the transmission matrix itself is not the information we are interested in, the equivalent channel parameters for each transmitted information symbols are calculated and the linear signal model for the information symbols is derived. Since that model is exactly the same as that of the coherent spatial multiplexing, all kinds of coherent detection schemes can be directly applied. The advantage of the proposed scheme over the differential space-time block codes (STBC) and the effects of scaling factor are investigated by computer simulation. In high transmission rate regimes, the proposed differential spatial multiplexing method can outperform the differential STBC having the same transmit rate in the signal to noise ratios (SNRs) we are interested in.

The tracking performance of the nonlinear carrier synchronizer in Rician fading channels is discussed. The performance is characterized in terms of the error variance of the estimated phase. Analytic results are provided using the joint probability density function (pdf) between two samples. These results are compared with those obtained by computer simulation in various fading conditions.

We propose a novel nonlinear model and a nonlinear equalizer for high density magnetic recording channels. The model is based on the superposition of data transition dependent pulses. The proposed nonlinear equalizer utilizes the proposed nonlinear model. When tested with actual read back signals, the model using 2 and 32 pulses achieved gains of 4.6 dB and 29.4 dB, respectively, over the linear model. Also the proposed nonlinear equalizer attained a gain of 1.5 dB over the RAM-DFE at a bit error rate of 1E10/sup -/6 when the nonlinear signal was generated by a finite state machine model.

In this paper, 60 GHz indoor broadband wireless channels are measured with various configurations in a typical office environment. Measurements are taken at nine positions of the room and the base-station antenna is placed either at the center or at an edge of the measurement room, and the remote-station antenna is of either sharp beam or broad beam type. The RMS delay spread (RDS) and normalized received power (NRP) are estimated from the measurements. Statistical models of the 60 GHz indoor wireless channels are also presented with model parameters from the measured channel data based on the Saleh's (1987) indoor channel modeling method. Bit error rate (BER) simulations are performed using measured and simulated channel impulse responses with DQPSK-OFDM modulation, respectively. Using sharp beam antenna results in superior performances to using broad beam antenna in terms of both bit error rates (BER) and NRP penalty. Also, placing the base-station antenna at the center is superior to placing it at an edge in terms of BER and NRP.