Residual Loss Rate Research Articles

Effects of seasonal changes on the carbon dynamics in mixed coniferous forests.

We investigated the residual rate and mass loss rate of litter, as well as the carbon release dynamics of litter and soil across seasons, to better understand the effects of seasonal fluctuations on carbon dynamics in mixed coniferous forests. The study was carried out in natural mixed coniferous forests in the Xiaoxinganling region of Heilongjiang Province, China, and the number of temperature cycles in the unfrozen season, freeze-thaw season, frozen season, and thaw season was controlled. The goal of the study was to examine how the carbon release dynamics of litter and soil respond to the freeze-thaw process and whether there are differences in carbon release dynamics under different seasons. Repeated-measures analysis of variance was used to analyze the residual mass rate and mass loss rate of litter, litter organic carbon and soil organic carbon during the unfrozen season, freeze-thaw season, frozen season, and thaw season. Litter decomposition was highest in the unfrozen season (15.9%~20.3%), and litter and soil carbon were sequestered throughout this process. Temperature swings above and below 0°C during the freeze-thaw season cause the litter to physically fragment and hasten its decomposition. Decomposition of litter was still feasible during the frozen season, and it was at its lowest during the thaw season (7.2%~7.8%), when its organic carbon was transported to the soil. Carbon migrates from undecomposed litter to semi-decomposed litter and then to soil. The carbon in the environment is fixed in the litter (11.3%~18.2%) and soil (34.4%~36.7%) in the unfrozen season, the carbon-fixing ability of the undecomposed litter in the freeze-thaw season is better, and the carbon in the semi-decomposed litter is mostly transferred to the soil; the carbon-fixing ability of the litter in the frozen season is worse (-3.9%~ -4.3%), and the organic carbon in the litter is gradually transferred to the soil. The carbon-fixing ability of the undecomposed litter in the thaw season is stronger, and the organic carbon in the semi-decomposed litter is mostly transferred to the soil. Both litter and soil can store carbon; however, from the unfrozen season until the thaw season, carbon is transported from undecomposed litter to semi-decomposed litter and to the soil over time.

Prediction of knock propensity using stochastic modeling in a spark-ignition engine

To comply with stringent CO2 regulations, enhanced thermal efficiency has been prioritized in internal combustion engine development; however, this has strongly driven the development of engines with operating conditions more prone to knock. Current knock sensors have its limitations to decompose knock signal by degradation so that it required a cross-referencing signal. In addition, knock control intervention is currently preceded by the occurrence of the knock, leading to decrease in thermal efficiency by retarding spark timing. In the present work, a novel prediction model for knock propensity (incidence) is presented, aiming to enable active control of knock or autoignition, and to support conventional knock sensor for cross-referencing by facilitating virtual knock sensor. A zero-dimensional model-based prediction of the in-cylinder pressure is demonstrated to prevent using in-cylinder pressure transducer, along with other incorporated predictive sub-models for the residual gas fraction, heat loss, burn duration, and heat release rate. Ignition delay correlation and Livengood-Wu relation are used to predict the onset of knock, and a burn point-based criterion is newly proposed for application in stochastic modeling for determining the knock propensity. The predicted knock propensity from the combined holistic model shows a remarkable agreement with experimental results.

Residual packet loss rate analysis of 2-D parity forward error correction

To improve the robustness of video communications over IP networks against packet losses, numerous IPTV and broadcasting standards have adopted the 2D application-layer forward error correction (FEC) method presented in Pro-MPEG COP3. This method uses a two-dimensional encoding matrix in which redundant checksums for each row and each column of the data matrix are generated and transmitted with the data packets. The approach has been recently extended and applied to layered video streaming. But despite its wide adoption and importance, a formal analysis of the correction performance of the Pro-MPEG COP3’s 2D FEC method is still lacking. In this paper, we formulate and solve the problem using an abstract mathematical framework, which can be used also for some natural extensions of this method. We derive tight bounds on the residual packet loss rate as a function of the 2D FEC matrix dimensions, and the packet loss rate assuming that the losses are independently and randomly distributed. We then provide simple approximations on these bounds for low packet loss rates. The analysis leads to the observation that the addition of a single checksum packet to the Pro-MPEG COP3 method would lead to a significant reduction in residual packet loss rate. The expressions derived are validated experimentally using Monte Carlo simulations. We also apply the results to the case of packet losses occurring in bursts. Finally, we study the impact of the matrix dimensions on the performance of the 2D FEC method, leading to valuable recommendations to system designers.

Experiment and Optimization of High-Efficiency Mechanical Separation of Peanut Seedlings and Residual Film Based on Suspension Velocity

HighlightsAn efficient method for separating peanut seedlings and residual film harvested from film-mulched peanut was proposed, and the mechanism was optimized.The relationships between the suspension velocity and moisture content of different shredded materials were studied.Four-factor, three-level Box-Behnken experiments were carried out and analyzed, and the optimal parameter combination was determined.A validation test was carried out to verify the rationality and accuracy of the optimized regression model.Abstract. To address the problems of lower residual film removal and higher material loss in the forage utilization of peanut seedlings wrapped in residual film, this study explored the relationships between the suspension velocity and moisture content of different shredded materials derived from peanut seedlings and conducted performance tests and parameter optimization for a machine that uses peanut seedlings as forage material. Four-factor, three-level Box-Behnken experiments were designed using the rotational speeds of the shredding shaft, upper fans, and lower fans and the frequency of the vibrating sieve as test factors, and using the residual film removal rate and material loss rate as response values. The test results indicated that the suspension velocity of the shredded materials showed a quadratic relationship with moisture content. The performance tests showed that the significance sequence of the test factors for the residual film removal rate was: rotational speed of the lower fans, rotational speed of the upper fans, rotational speed of the shredding shaft, and frequency of the vibrating sieve. The significance sequence for the material loss rate was: rotational speed of the lower fans, rotational speed of the shredding shaft, frequency of the vibrating sieve, and rotational speed of the upper fans. The parameter optimization and validation test showed that the residual film removal rate was 92.71% and the material loss rate was 8.19% when the rotational speeds of the shredding shaft, upper fans, and lower fans were 1650, 770, and 665 rpm, respectively, and the frequency of the vibrating sieve was 4 Hz. The relative errors between the validation test results and the predicted values from the regression models were less than 3%, which suggests that the regression models are reliable. This study provides a reference for the forage utilization of peanut seedlings harvested from film-mulched peanut and provides a reference for determining the optimal working parameters of forage processing machines. Keywords: Agricultural machinery, Box-Behnken experiment, Optimization, Peanut film-seedling separation, Suspension velocity.

Effect of curing regime on water resistance of magnesium–potassium phosphate cement

In this paper, the effects of curing conditions (dry air, moist air and water), state of water (static water and flowing water) and initial air curing time (5h, 3d and 28d) on the corrosion behavior of magnesium–potassium phosphate cement (MKPC) paste subjected to water attack were investigated. The strength residual ratio and mass loss rate were used as deterioration indexes of MKPC paste in water. The pH value and leaching amounts of soaking liquid were also employed to evaluate the water corrosion behavior. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetry analysis (TG) and mercury intrusion porosimetry (MIP) were used to investigate the microstructure of MKPC paste before and after water corrosion. The experimental results showed that the water environment lead to a lower compressive strength of MKPC pastes, but the strength loss of MKPC paste under the flowing water curing was higher. Furthermore, prolonged initial air curing time could improve the water resistance of MKPC pastes, the specimens cured in air for the first 3days then in water showed the best water resistance among all specimens immersed in water for 60days. The deterioration mechanism of MKPC paste derived from the strength and mass loss test results was also clarified based on microstructural observation.

Peer-to-peer error recovery for wireless video broadcasting

Wireless video broadcasting has experienced much growth in recent years. In video broadcasting, packet loss is inevitable due to dynamic channel condition. To address this, we study peer-to-peer (P2P) error recovery. In our system, a mobile station (MS) may generate some parity packets based on its received source packets and share them by broadcasting to its neighbors via a secondary channel (e.g., Wi-Fi or Bluetooth). With parity packets from its neighbors, an MS can effectively repair its lost packets locally. An important problem is to minimize the total number of parity packets generated while achieving a certain residual loss rate at the MSs. We first formulate the problem as a linear program which can be solved efficiently as the optimal performance of the system. We then propose a novel and fully distributed algorithm based on only local information at clients. Simulation results show that our distributed solution achieves high recovery efficiency and fast convergence. It generates very low recovery traffic and high video quality. Its performance is very close to the optimal solution based on centralized approach with complete network information.

Performance Analysis of VoIP by Communicating Two Systems

VoIP is a technology that digitizes voice packets and enables telephony communication by using internet as a backbone. In this paper we introduce and explore the problems that occur in our day to day life in sending voice and data with different windows. The paper evolves in the VoIP environment. Sending of text and voice along single window is possible. In earlier days VoIP merges over devices like IP Telephony, Palms, PDAs, etc over IP network for communication. But less security is provided with packet loss, retransmission, end to end delay and overhead. VoIP is composed of Signalling and Media. The use of Signalling is for controlling communication and it does the call set up, locate users, and tear down sessions. Media is used for transporting the voice packets. Ad hoc wireless networks are formed by a set of mobile nodes that communicate with each other over a wireless channel. Perceived Voice Quality can be achieved in terms of NS-2 Simulator. The work focuses with the combined forward error correction, layered coding and multiple. VoIP is a term used for a set of facilities for managing the delivery of voice information using the Internet Protocol. With VoIP there is no dedicated connection between the communicating devices. In addition to IP VoIP uses parameters such as residual packet loss rate and average burst length for secured delivery of voice and data. The protocols used are SIP and RTP. Our task in this work is to configure and create the test bed to simulate the working of Voice over IP (VoIP) Network. Also detailed and scrutinized study is made to test the performance of the proposed configuration. Two systems are installed with Client software and the third one with Server and the settings are made in such a way that Call from Client A will pass to the server and then server transfers to client B. NS-2 is used to analyse the network communication among the three machines

Performance Analysis of Systematic Upper Layer FEC Codes and Interleaving in Land Mobile Satellite Channels

This paper provides an analytical method for evaluating the performance of upper layer forward error correction (FEC), when used together with interleaving on land mobile satellite channels, in terms of residual (after decoding) packet loss rate (PLR). In addition, the analysis highlights the overheads introduced by this technique, which depend on the channel statistics, in terms of additional packet delivery delay, bandwidth consumption, and computation power required. We show why the interleaver is mandatory in some environments, due to the severe disruptive characteristics of the channel, according to measurement campaigns promoted by the European Space Agency. This analysis provides the expression of the residual PLR when systematic FEC coding blocks are interleaved at the packet level (i.e., when a cyclic redundancy check and a sequence number identify a correct data unit). This method can be employed for the performance evaluation of recent and future mobile communication systems that take advantage of upper layer FEC and interleaving techniques.

Customized Forwarding in application layer multicast for real-time services

We propose a customized forwarding (CF) scheme for tree-based application layer multicasts to support real-time interactive multimedia services. We show that CF reduces residual loss rate and play pause frequency significantly.

Flexible forward error correction codes with application to partial media data recovery

Conventionally, linear block codes designed for packet erasure correction are targeted to recover all the lost source packets per block, when the fraction of lost data is smaller than the redundancy overhead. However, these codes fail to recover any lost packets, if the number of erasures just exceeds the limit for full recovery capability, while it can still be beneficial to recover part of the symbols. In addition, common linear block codes are not well suited for unequal error protection, since different block codes with different rates must be allocated for each priority class separately. These two problems motivate the design of more flexible forward error correction (FEC) codes for media streaming applications. We first review the performance of short and long linear block codes. Long block codes generally offer better error correction capabilities, but at the price of higher complexity and larger coding delay. Short block codes can be more appropriate in media streaming applications that require smooth performance degradation when the channel loss rate increases. We study a new class of linear block codes using sparse generator matrices that permit to optimize the performance of short block codes for partial recovery of the lost packets. In addition, the proposed codes are extended to the design of unequal erasure protection solutions. Simulations of practical video streaming scenarios demonstrate that the flexible sparse codes offer a promising solution with interesting error correction capabilities and small variance in the residual loss rate. They typically represent an effective trade-off between short block codes with limited flexibility, and long block codes with delay penalties.

Fish farming enhances biomass and nutrient loss in Posidonia oceanica (L.) Delile

Fish farming impact on the seasonal biomass, carbon and nutrient (nitrogen and phosphorus) balance of the endemic Mediterranean seagrass Posidonia oceanica was assessed in the Aegean Sea (Greece) in order to detect changes in magnitude and fate of seagrass production and nutrient incorporation with organic loading of the meadows. Phosphorus concentration in the leaves, rhizomes and roots was enhanced under the cages throughout the study. Standing biomass was diminished by 64% and carbon, nitrogen and phosphorus standing stock by 64%, 61% and 48%, respectively, under the cages in relation to those at the control. Seagrass production decreased by 68% and element (C, N, P) incorporation by 67%, 58% and 58%, respectively, under the cages. Leaf shedding was reduced by 81% and loss of elements (C, N, and P) through shedding by 82%, 74% and 72%, respectively, under the cages. Leaf and element (C, N, P) residual loss rate, accounting for grazing and mechanical breakage of leaves, was decreased by 79%, 85%, 100% and 96%, respectively, at the control station. At the control station, 13.98 g C m −2 yr −1, 1.91 g N m −2 yr −1 and 0.05 g P m −2 yr −1 were produced in excess of export and loss. In contrast, under the cages 12.69 g C m −2 yr −1, 0.31 g N m −2 yr −1 and 0.04 g P m −2 yr −1 were released from the meadow. Organic loading due to fish farm discharges transformed the seagrass meadow under the cages from a typical sink to a source of organic carbon and nutrients.

Effect of air preheating and fuel moisture on combustion characteristics of corn straw in a fixed bed

Experiments were carried out on a one-dimensional bench combustion tests rig. The effect of air preheating and moisture level in the fuel on combustion characteristics of corn straw was investigated. The bed temperature distribution and the mass loss of fuel and gas components such as O 2, CO, CO 2 and NO were measured in the bed. The average burning rate and ignition front propagation velocity increased with increasing primary air preheating temperature. The total burning time was shorter under the higher primary air preheating temperature and the higher primary air preheating temperature produced a lower ignition front flame temperature in the bed. The variation of the flue gas O 2, CO and CO 2 concentrations with time was more intensive at a higher primary air preheating temperature during the ignition front propagation period and the char oxidation period. With the increase of the fuel moisture, average burning rate and ignition front propagation velocity decreased. As the fuel moisture was less than 30.71%, with the increase of the fuel moisture, residual mass loss rate decreased and ignition front flame temperature increased at a fixed air flow rate. Drier fuels resulted in fuel-rich combustion and higher CO concentration. The NO concentration decreased with increasing the moisture level in the fuel.

Generic forward error correction of short frames for IP streaming applications

If the frame size of a multimedia encoder is small, Internet Protocol (IP) streaming applications need to pack many encoded media frames in each Real-time Transport Protocol (RTP) packet to avoid unnecessary header overhead. The generic forward error correction (FEC) mechanisms proposed in the literature for RTP transmission do not perform optimally in terms of stability when the RTP payload consists of several individual data elements of equal priority. In this paper, we present a novel approach for generating FEC packets optimized for applications packing multiple individually decodable media frames in each RTP payload. In the proposed method, a set of frames and its corresponding FEC data are spread among multiple packets so that the experienced frame loss rate does not vary greatly under different packet loss patterns. We verify the performance improvement gained against traditional generic FEC by analyzing and comparing the variance of the residual frame loss rate in the proposed packetization scheme and in the baseline generic FEC.

Lateral error recovery for media streaming in application-level multicast

We consider media streaming using application-level multicast (ALM) where packet loss has to be recovered via retransmission in a timely manner. Since packets may be lost due to congestion, node failures, and join and leave dynamics, traditional "vertical" recovery approach where upstream nodes retransmit the lost packets is no longer effective. We therefore propose lateral error recovery (LER). In LER, hosts are divided into a number of planes, each of which forms an independent ALM tree. Since error correlation across planes is low, a node effectively recovers its error by "laterally" requesting retransmission from nearby nodes in other planes. We present analysis on the complexity and recovery delay on LER. Using Internet-like topologies, we show via simulations that LER is an effective error recovery mechanism. It achieves low overhead in terms of delivery delay (i.e., relative delay penalty) and physical link stress. As compared with traditional recovery schemes, LER attains much lower residual loss rate (i.e., loss rate after retransmission) under a certain deadline constraint. The performance can be substantially improved in the presence of some reliable proxies.

Monte Carlo simulation of scanning electron microscope signals for lithographic metrology

AbstractTwo computer codes for simulating the backscattered, transmitted, and secondary‐electron signals from targets in a scanning electron microscope are described. The first code, MONSEL‐II, has a model target consisting of three parallel lines on a three‐layer substrate, while the second, MONSEL‐III, has a model target consisting of a two‐by‐two array of finite lines on a three‐layer substrate. Elastic electron scattering is determined by published fits to the Mott cross section. Both plasmon‐generated electrons and ionized valence electrons are included in the secondary production. An adjustable quantity, called the residual energy loss rate, is added to the formula of Joy and Luo to obtain the measured secondary yield. The codes show the effects of signal enhancement due to edge transmission, known as blooming, as well as signal reduction due to neighboring lines, known as the “black‐hole” effect.