Dead Spots Research Articles

Patient motion tracking for non-isocentric and non-coplanar treatments via fixed frame-of-reference 3D camera.

PurposeAs C‐arm linac radiation therapy evolves toward faster, more efficient delivery, and more conformal dosimetry, treatments with increasingly complex couch motions are emerging. Monitoring the patient motion independently of the couch motion during non‐coplanar, non‐isocentric, or dynamic couch treatments is a key bottleneck to their clinical implementation. The goal of this study is to develop a prototype real‐time monitoring system for unconventional beam trajectories to ensure a safe and accurate treatment delivery.MethodsAn in‐house algorithm was developed for tracking using a couch‐mounted three‐dimensional (3D) depth camera. The accuracy of patient motion detection on the couch was tested on a 3D printed phantom created from the body surface contour exported from the treatment planning system. The technique was evaluated against a commercial optical surface monitoring system with known phantom displacements of 3, 5, and 7 mm in lateral, longitudinal, and vertical directions by placing a head phantom on a dynamic platform on the treatment couch. The stability of the monitoring system was evaluated during dynamic couch trajectories, at speeds between 10.6 and 65 cm/min.ResultsThe proposed monitoring system agreed with the ceiling mounted optical surface monitoring system in longitudinal, lateral, and vertical directions within 0.5 mm. The uncertainty caused by couch vibration increased with couch speed but remained sub‐millimeter for speeds up to 32 cm/min. For couch speeds of 10.6, 32.2, and 65 cm/min, the uncertainty ranges were 0.27– 0.73 mm, 0.15–0.87 mm, and 0.28–1.29 mm, respectively.ConclusionBy mounting a 3D camera in the same frame‐of‐reference as the patient and eliminating dead spots, this proof of concept demonstrates real‐time patient monitoring during couch motion. For treatments with non‐coplanar beams, multiple isocenters, or dynamic couch motion, this provides additional safety without additional radiation dose and avoids some of the complexity and limitations of room mounted systems.

Fusion of Nonintrusive Environmental Sensors for Occupancy Detection in Smart Homes

We presented an approach to detect and count occupants using a fusion of environmental sensors from an indoor air quality measurement system. Environmental sensors, as opposed to motion detectors, are nonintrusive, easy to install, low cost, detect nonmoving occupants, do not have dead spots, and can even infer the number of occupants. For this paper, we conducted measurements of carbon dioxide, volatile organic compounds (VOCs), air temperature, and air relative humidity in four student apartments for a total of 49 days. We extracted features from the environmental sensors and selected subsets using correlation-based feature selection. Subsequently, we performed a comparison of the supervised learning models repeated incremental pruning to produce error reduction, naive Bayes (NB), C4.5 decision tree, logistic regression, ${k}$ -nearest neighbors, and random forest. We further proposed a method to greatly reduce time and effort of collecting training data in residential buildings. The results indicated that the predictive power of VOC sensing is comparable to that of carbon dioxide. With a simple NB classifier, our approach detected occupancy and estimated the number of occupants with an accuracy of 81.1 % and 64.7 %, respectively.

Contact Interruptions (2003)

Contact Interruptions (2003)

Discovery of a Sweet Spot on the Foot with a Smart Wearable Soccer Boot Sensor That Maximizes the Chances of Scoring a Curved Kick in Soccer.

This paper provides the evidence of a sweet spot on the boot/foot as well as the method for detecting it with a wearable pressure sensitive device. This study confirmed the hypothesized existence of sweet and dead spots on a soccer boot or foot when kicking a ball. For a stationary curved kick, kicking the ball at the sweet spot maximized the probability of scoring a goal (58–86%), whereas having the impact point at the dead zone minimized the probability (11–22%). The sweet spot was found based on hypothesized favorable parameter ranges (center of pressure in x/y-directions and/or peak impact force) and the dead zone based on hypothesized unfavorable parameter ranges. The sweet spot was rather concentrated, independent of which parameter combination was used (two- or three-parameter combination), whereas the dead zone, located 21 mm from the sweet spot, was more widespread.

Systematization and comparative scheme analysis of mechanisms of planetary rotary hydraulic machines

The systematization of planetary rotary hydraulic machines (PRHM) with floating rollers is presented in the article. This systematization is carried out according to such structural features as: the number of waves that have central tooth gears with internal and external teeth, the character of the leading link motion; selection of a supporting (fixed) link; selection of the link containing the channels. The systematization allows us to list all essentially different schemes of PRHM and conduct their comparative analysis. The comparison is based on such technical parameters as: symmetry of schemes; absence of dead spots; PRHM performance, pulsation of instantaneous performance; channel cross-sectional area. The comparison showed that based on a set of indicators, the schemes with the numbers of central wheel waves 2×4; 4×6; 6×8 are preferred, in which the rotor performs a purely rotary motion.

DMAD

Wireless networks offer many advantages over wired local area networks such as scalability and mobility. Strategically deployed wireless networks can achieve multiple objectives like traffic offloading, network coverage, and indoor localization. To this end, various mathematical models and optimization algorithms have been proposed to find optimal deployments of access points (APs). However, wireless signals can be blocked by the human body, especially in crowded urban spaces. As a result, the real coverage of an on-site AP deployment may shrink to some degree and lead to unexpected dead spots (areas without wireless coverage). Dead spots are undesirable, since they degrade the user experience in network service continuity, on one hand, and, on the other hand paralyze some applications and services like tracking and monitoring when users are in these areas. Nevertheless, it is nontrivial for existing methods to analyze the impact of human beings on wireless coverage. Site surveys are too time consuming and labor intensive to conduct. It is also infeasible for simulation methods to predict the number of on-site people. In this article, we propose DMAD, a Data-driven Measuring of Wi-Fi Access point Deployment, which not only estimates potential dead spots of an on-site AP deployment but also quantifies their severity, using simple Wi-Fi data collected from the on-site deployment and shop profiles from the Internet. DMAD first classifies static devices and mobile devices with a decision-tree classifier. Then it locates mobile devices to grid-level locations based on shop popularities, wireless signal, and visit duration. Last, DMAD estimates the probability of dead spots for each grid during different time slots and derives their severity considering the probability and the number of potential users. The analysis of Wi-Fi data from static devices indicates that the Pearson Correlation Coefficient of wireless coverage status and the number of on-site people is over 0.7, which confirms that human beings may have a significant impact on wireless coverage. We also conduct extensive experiments in a large shopping mall in Shenzhen. The evaluation results demonstrate that DMAD can find around 70% of dead spots with a precision of over 70%.

CFD Analysis of Thermal Distribution in the Industrial Fermenter duringSterilization Process

In biological reactors, isolation of unwanted microorganisms by using sterilization is essential. One of the important reasons of microbial contamination in industrial fermenter is bioreactor poor design which causes to create dead spot during sterilization. Therefore, identifying the dead spots in the sterilization process is crucial which could be accomplished by computational fluid dynamics (CFD). In this study, for identifying the spots which their thermal distributions are not uniform (due to fermenter geometry deficiency), the sterilization process in a 140 m3 fermenter (without culture media) were modeled (129-133°C and 15 min). Study of temperature profile, velocity and stream lines shows that in the manhole, around the coils, steam inputs and below the impeller on the agitator shaft are the places that the risk of dead spot creation is high.

Wireless Information and Power Transfer Design for Energy Cooperation Distributed Antenna Systems

Distributed antenna systems (DAS) have been widely implemented in state-of-the-art cellular communication systems to cover dead spots. Recent studies have also indicated that DAS have advantages in wireless energy transfer (WET). In this paper, we study simultaneous wireless information and power transfer (SWIPT) for a multiple-input single-output (MISO) DAS in the downlink which consists of arbitrarily distributed remote antenna units (RAUs). In order to save the energy cost, we adopt energy cooperation of energy harvesting (EH) and two-way energy flows to let the RAUs trade their harvested energy through the smart grid network. Under individual EH constraints, per-RAU power constraints and various smart grid considerations, we investigate a power management strategy that determines how to utilize the stochastically spatially distributed harvested energy at the RAUs and how to trade the energy with the smart grid simultaneously to supply maximum wireless information transfer (WIT) with a minimum WET constraint for a receiver adopting power splitting (PS). Our analysis shows that the optimal design can be achieved in two steps. The first step is to maximize a new objective that can simultaneously maximize both WET and WIT, considering both the smart grid profitable and smart grid neutral cases. For the grid-profitable case, we derive the optimal full power strategy and provide a closed-form result to see under what condition this strategy is used. On the other hand, for the grid-neutral case, we illustrate that the optimal power policy has a double-threshold structure and present an optimal allocation strategy. The second step is then to solve the whole problem by obtaining the splitting power ratio based on the minimum WET constraint. Simulation results are provided to evaluate the performance under various settings and characterize the double-threshold structure.

О физической природе возникновения дефектов типа «матовые пятна» при контактной сварке магистральных трубопроводов из феррито-перлитных сталей

О физической природе возникновения дефектов типа «матовые пятна» при контактной сварке магистральных трубопроводов из феррито-перлитных сталей

Tin nanoparticles as an effective conductive additive in silicon anodes.

We have found that the addition of tin nanoparticles to a silicon-based anode provides dramatic improvements in performance in terms of both charge capacity and cycling stability. Using a simple procedure and off-the-shelf additives and precursors, we developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface. Even a minor addition of tin, as small as ∼2% by weight, results in a significant decrease in the anode resistance, as confirmed by electrochemical impedance spectroscopy. This leads to a decrease in charge transfer resistance, which prevents the formation of electrically inactive “dead spots” in the anode structure and enables the effective participation of silicon in the lithiation reaction.

Relay Multi-hop Communications for Next Generation Mobile Networks: Investigation of Path-Loss Models

In next generation communication systems, a multi-hop scheme, in which stations between a mobile terminal and a base station relay signal transmissions, seems a promising ap-proach for wide-area coverage and system capacity enhancement. Another prospective benefit for multi-hop scheme is the reduction of transmission power for a link. This reduction is expected by splitting the transmission into a series of hops using the other mobile stations as repeaters which provide a gain from receiver (Rx) to transmitter (Tx). In this way, the transmission power is expected to become less due to the non-linear nature of the path loss. In this work, different path loss models are examined for multi-hop communication systems. Direct communication and the multi-hop communication cases are compared according to different path loss models. The question of how path loss changes by splitting the transmission into a series of sub-paths is also investigated. The investigations show that it is not possible to reduce the path losses except for some cases thus the transmit power. On the other hand using the multi-hop scheme makes possible to increase the coverage area of the network and also reduce the dead spots in the cell.

Enhancing the Performance of Indoor Device-Free Passive Localization

Device-free passive localization (DFPL) has been an emerging application with fast increasing development. Channel State Information- (CSI-) based DFPL is recently paid more attention to for fine-granularity and stability of CSI. However, lots of dead spots exist in the area of interest. And the accuracy of localization is not still completely satisfactory, especially for outside of the first Fresnel zone. In our paper, we put forward a new metric to estimate the sensitivity of a receiver to changes in the detecting area. In our experiment, we observe that the performance of DFPL can be raised when the receiver is placed at the location with high receiver sensitivity. Hence, we develop a new high-performance indoor device-free passive localization (HiDFPL), which employs a Bayesian a posteriori approach and possesses high receiver sensitivity. The experiment results demonstrate the outstanding performance of the proposed scheme.

Identification of surgical instruments using UHF-RFID technology

Abstract The paper presents research, development and advantage of Radio Frequency IDentification (RFID) technology based system for medical instrument management and safe usage. The system is developed for two scenarios. In the first scenario, a Ultra High Frequency (UHF) is used and the UHF–interrogator system with UHF-antennas is constructed to work as conveyor-belt and instruments are placed between two antennas. Second scenario, suitable for the operating rooms, includes four antennas, placed under the table with instruments, system’s phase shifter, inserted between the antenna and reader in order to reduce the effect of dead spots, caused by the electromagnetic reflections. High reliable identification rate is achieved by synchronizing phase shifters with particular interrogator. The system is software calibrated and can be re-calibrated at run-time to achieve high efficiency of power transmission to the antenna and in order to enable the receiver to decode the tag signals. With currently on the market available RFID tags and previously mentioned technology approaches, detection rate of 87.5% can be achieved.

융복합 기술을 이용하는 컨테이너 항만에서 야드 트랙터에 탑재된 웹-패드의 무선통신 환경 개선 방안

Abstracts The container terminals use convergence technology that exchange information for cargo work, using wireless communication between the TOS(Terminal Operations System) and the handling equipments(CC, TC, YT). But if the container cargoes pile up high in the container yard, delayed cargo work and cargo working list information error happen because of communication dead spots(the worker can not receive the information) which wireless communication is disconnected. At this time the driver of the yard tractor(YT) must be able to recognize the communication state. If then, delayed cargo work and cargo working list information errors that occur in the shaded communication area can be avoided, and can process the delayed work due to wireless communication break. In this project, we have built wireless communication environment to increase the efficiency of the loading and unloading operations which the operator can respond actively, when the work is delayed and work orders result in errors. That is, the flow of the wireless communication module has been changed.

When “homogeneity” is expected—Theory of Sampling in pharmaceutical manufacturing

Author Summary: A stream sampling method has been developed to facilitate implementation of variographic analysis and use of replication experiments in the development of pharmaceutical formulations. These methods are thoroughly developed in the Theory of Sampling but are not currently used in pharma. Pharmaceutical formulations have very strict requirements as drug products are expected to deliver a specific drug content to patients and are required to avoid possible consequences of over-dosing or under-dosing. Formulation developers currently rely on grab sampling, the use of a sample thief (spear) to extract material from areas suspected of having incomplete mixing (“dead spots”). This study applies an alternative stream sampling approach based on the Theory of Sampling in connection with testing two alternative mixing processes. The mixing process based on vibration and tumbling can be shown to provide a significantly lower end-point heterogeneity. The results show the usefulness of the variographic approach in combination with replication experiments; both are effective in identifying areas of unacceptable heterogeneity in pharmaceutical blends, and point to the need to continue improving the mixing processes described in this study.

Downlink performance of two‐tier networks with time‐hopping modulation

With growing demand for high data rates, the mobile network has faced excessive traffic and it seems that one of the few long-term solutions to this problem is employing femtocells which improve capacity and indoors coverage. In the typical femtocell networks, co- and cross-layer interferences caused by simultaneous transmission of macrocell base stations and femtocell access points in the same frequency band, results in dead spots especially if femtocells are densely employed. In this study, to mitigate the interference and improve the system's performance, the authors study the application of time-hopping approach. Particularly, the impact of aggressive signals of femto access points on a macro user equipment located in the second tier, that is, the femtocell coverage area, is analysed and the semi-closed-form expression for the system outage probability is derived. Based on the analysis, they also simulate the transmission capacity (TC) that represents the total capacity of the co-channel two-tier networks with outage constraints. Next, employing Gaussian approximations, they derive upper and lower bounds on the outage probability. These bounds provide better insight on the effect of system's parameters on its performance. Their numerical results show that the time-hopping technique significantly reduces the outage probability and therefore increases the TC of two-tier networks.

The application of computational fluid dynamics and small-scale physical models to assess the effects of operational practices on the risk to public health within large indoor swimming pools

Swimming pools provide an excellent facility for exercise and leisure but are also prone to contamination from microbial pathogens. The study modelled a 50-m × 20-m swimming pool using both a small-scale physical model and computational fluid dynamics to investigate how water and pathogens move around a pool in order to identify potential risk spots. Our study revealed a number of lessons for pool operators, designers and policy-makers: disinfection reaches the majority of a full-scale pool in approximately 16 minutes operating at the maximum permissible inlet velocity of 0.5 m/s. This suggests that where a pool is designed to have 15 paired inlets it is capable of distributing disinfectant throughout the water body within an acceptable time frame. However, the study also showed that the exchange rate of water is not uniform across the pool tank and that there is potential for areas of the pool tank to retain contaminated water for significant periods of time. 'Dead spots' exist at either end of the pool where pathogens could remain. This is particularly significant if there is a faecal release into the pool by bathers infected with Cryptosporidium parvum, increasing the potential for waterborne disease transmission.

Composite Effect of E/O Nonlinearity and Optical Echo on EPWM-OFDM Transmission in Radio Over Fiber Channel

Radio over Fiber (RoF) is a promising technology for extending broadband wireless access to indoor and outdoor dead spots. However, commonly applied intensity-modulation / direct-detection RoF transmission presents some nonlinearity and produces echo distortion. Since multiple carrier modulation signals such as Orthogonal Frequency Division Multiplexing (OFDM) are widely employed in broadband wireless systems, the above issues become more serious. The OFDM signals have high Peak-to-Average Power Ratio, which makes them more sensitive to nonlinearity. Moreover, the large delay of optical echoes that are caused by the discontinuity of refractive index at both ends of Electrical/Optical (E/O) and Optical/Electrical converters exceeds the guard time of current OFDM symbols when the length of optical fiber is long. Since the nonlinearity and echo exist simultaneously in RoF channels, their composite effect is mathematically analyzed in this paper. A RoF-echo model is proposed for the modeling of the multiple light reflections and its validity is confirmed by experiments. Then, Envelop-Pulse-Width-Modulation- (EPWM-) RoF transmission is proposed for dealing with the nonlinearity and echo in RoF channel. The performance of the EPWM-RoF scheme for OFDM signal transmission is evaluated by simulations, which reveals that the scheme improves the transmission quality in Error Vector Magnitude under the composite environment of E/O nonlinearity and optical echo.

QoS-guaranteed Mobile IPTV service in heterogeneous access networks

Internet Protocol Television is defined as a multimedia service delivered over IP-based networks supporting quality of service (QoS), quality of experience (QoE), security, interactivity, and reliability. This service is rapidly expanding to both wireless and mobile networks through mobile devices. This trend demands a seamless IPTV service architecture for those mobile devices in heterogeneous access networks. This is because the convergence of the heterogeneous access networks can resolve their own service-coverage limitations, eliminating dead spots. We first briefly research on the background and trend for the seamless IPTV service for heterogeneous networks. Next we propose a new system architecture taking the relevant technical issues into account. This architecture is mainly composed of three parts, (i) information of network conditions on client, (ii) signaling for communicating between client and server with information of network conditions, and (iii) adaptive streaming based on information of network conditions. The proposed architecture can be deployed on any Internet protocol layers such as application layer, transport layer and network layer. In this paper, we evaluate two cases such as (i) RTSP in application layer and (ii) SCTP in transport layer and compare them through the performance evaluation. The results in the evaluation show that the proposed architecture meets well the requirements of the minimum IPTV service performance recommended by ITU-T international standard for the QoE over heterogeneous access networks.

The humanist moment

In “The Humanist Moment,” Chris Higgins sets out to recover a tenable, living humanism, rejecting both the version vilified by the anti-humanists and the one sentimentalized by the reactionary nostalgists. Rescuing humanism from such polemics is only the first step, as we find at least nine rival, contemporary definitions of humanism. Which movement or theory is the real humanism? Higgins contends that we can reconstruct a critical, dialectical humanism from the very tensions in these conceptions. On this view, humanism is neither a theory nor a movement, but a moment, a specific intervention evincing characteristic sensibilities, enabling us to navigate through one of a number of recurring dead spots in the life of culture. Higgins outlines four ongoing human dialectics whose vibrant center the humanist helps us regain: genuine hope/acceptance in the face of both fantasy and cynicism; combined awareness of our connectedness and distinctiveness rejecting both dogmatic universalizing and particularizing discourses; and humane learning as distant from scholasticism as it is from anti-intellectualism. An entire section is devoted to the fourth dialectic, showing how humanism has appeared as a corrective both to historicism and to presentism, helping us reconnect with the untimely, living voice of tradition.