Upstream Channel Research Articles

SCHC over LoRaWAN Efficiency: Evaluation and Experimental Performance of Packet Fragmentation.

Low Power Wide Area Networks (LPWAN) are expected to enable the massive connectivity of small and constrained devices to the Internet of Things. Due to the restricted nature of both end devices and network links, LPWAN technologies employ network stacks where there is no interoperable network layer as a general case; instead, application data are usually placed directly into technology-specific two-layer frames. Besides not being able to run standard IP-based protocols at the end device, the lack of an IP layer also causes LPWAN segments to operate in an isolated manner, requiring middleboxes to interface non-IP LPWAN technologies with the IP world. The IETF has standardized a compression and fragmentation scheme, called Static Context Header Compression and Fragmentation (SCHC), which can compress and fragment IPv6 and UDP headers for LPWAN in a way that enables IP-based communications on the constrained end device. This article presents a model to determine the channel occupation efficiency based on the transmission times of SCHC messages in the upstream channel of a LoRaWAN™ link using the ACK-on-Error mode of standard SCHC. The model is compared against experimental data obtained from the transmission of packets that are fragmented using a SCHC over LoRaWAN implementation. This modeling provides a relationship between the channel occupancy efficiency, the spreading factor of LoRa™, and the probability of an error of a SCHC message. The results show that the model correctly predicts the efficiency in channel occupation for all spreading factors. Furthermore, the SCHC ACK-on-Error mode implementation for the upstream channel has been made fully available for further use by the research community.

Geospatial assessment of water quality using principal components analysis (PCA) and water quality index (WQI) in Basho Valley, Gilgit Baltistan (Northern Areas of Pakistan).

Public health quality in Gilgit Baltistan (GB) is at threat due to multiple water-borne diseases. Anthropogenic activities are accelerating the burden of pollution load on the glacio-fluvial streams and surface water resources of Basho Valley in Skardu district of GB. The present research has investigated the drinking water quality of the Basho Valley that is being used for domestic purposes. The study also comprehends public health status by addressing the basis drinking water quality parameters. A total of 23 water samples were collected and then analyzed to elucidate the current status of physico-chemical, metals, and microbial parameters. Principal component analysis (PCA) was applied and three principal components were obtained accounting 53.04% of the total variance, altogether. PCA identified that metallic and microbial parameters are the major factor to influence the water quality of the valley. Meanwhile, water quality index (WQI) was also computed and it was observed that WQI of the valley is characterized as excellent in terms of physico-chemical characteristics; however, metals and microbial WQI shows most of the samples are unfit for drinking purpose. Spatial distribution is also interpolated using the Inverse distance weight (IDW) to anticipate the results of mean values of parameters and WQI scores. The study concludes that water quality is satisfactory in terms of physico-chemical characteristics; however, analysis of metals shows that the concentrations of copper (Cu) (0.40 ± 0.16mg/L), lead (Pb) (0.24 ± 0.10mg/L), zinc (Zn) (6.77 ± 27.1mg/L), manganese (Mn) (0.19 ± 0.05), and molybdenum (Mo) (0.07 ± 0.02mg/L) are exceeding the maximum permissible limit as set in the WHO guidelines for drinking water. Similarly, the results of the microbial analysis indicate that the water samples are heavily contaminated with fecal pollution (TCC, TFC, and TFS > 3 MPN/100mL). On the basis of PCA, WQI, and IDW, the main sources of pollution are most likely to be concluded as the anthropogenic activities including incoming pollution load from upstream channels. A few underlying sources by natural process of weathering and erosion may also cause release of metals in surface and groundwater. This study recommends ensuring public health with regular monitoring and assessment of water resources in the valley.

Long-Distance Pipe Jacking in Complex Urban Geological Environment

A steel underground pipeline with a diameter of 2.4 m and a total length of 3,617 m (plate thickness of 26 mm) has been constructed in a city in central Hubei, and the engineering, procurement, and construction (EPC) project has been lifted from the upstream channel to supplement water to the downstream lake inside the city. Through preliminary geological survey data, site topographic and geomorphic survey, urban construction, as well as the requirements of the construction party, the preliminary arrangement of working wells and receiving wells as well as the selection and customization of pipe jacking machines have been proposed. Frequency conversion motor and remote monitoring technology are adopted for geotechnical change and long-distance pipe jacking. Through detailed survey, the rock and soil change section as well as gradual change conditions have been determined, the accuracy of construction mechanics calculation and construction operation control have improved, the basis and analysis basis are provided, and some experiences in construction operation are summarized.

Determining the seasonal relationships between upstream flows and channel transmission losses along a dryland river reach

River transmission loss is the reduced amount of flow at downstream locations along a channel due to infiltration into the riverbed and riverbank, evaporation from water surface, transpiration by riparian vegetation and, temporary storage in the river and flood plains. Transmission losses reduce flood stage, recharge local and regional aquifers and, are main sources of groundwater recharge in dryland areas. This study determines the seasonal relationships between upstream flows and channel transmission losses along a river reach in Runde River catchment in Zimbabwe. Using regression equations, channel transmission loss volumes were modelled as the response variables while upstream flow volumes were the predictor variables. The study shows significant (p = 0.000) positive linear relationships between reach upstream flow and transmission loss during the cool, hot and rainy seasons. Also, during the post rainy season, a significant (p = 0.000) power relationship exist between reach upstream flow and transmission loss. This simple approach helps to understand water balances and transmission losses in data scarce dryland river systems.

Determining the seasonal relationships between upstream flows and channel transmission losses along a dryland river reach

Determining the seasonal relationships between upstream flows and channel transmission losses along a dryland river reach

High Bandwidth Utilization DWBA Algorithm for Upstream Channel in NG-EPON

In this paper, an (ONU-load and RTTs)-based (OLR) dynamic wavelength and bandwidth allocation (DWBA) algorithm for upstream channel in next-generational Ethernet passive optical network (NG-EPON) is proposed. By proposing adaptive threshold grouping algorithm, the waste of bandwidth resources caused by massive guard timeslots and mismatch between assigned transmission window and frame size is reduced. By adjusting the Optical Network Unit (ONU) scheduling order, the idle time caused by Round-Trip Times (RTTs) is reduced. By proposing joint ONU grouping and RTT scheduling mechanism, load balance among wavelengths is achieved. By proposing a fair allocation scheme, the fairness of bandwidth granting for each ONU is ensured. Finally, by the simulation, the effectiveness of proposed algorithm is demonstrated. The simulation indicates that the rate of bandwidth utilization, the average package delay, the scheduling cycle and the network throughput in the system based on proposed algorithm have better performance.

Strontium isotope dynamics reveal streamflow contributions from shallow flow paths during snowmelt in a montane watershed, Provo River, Utah, USA

AbstractQuantifying the routing of snowmelt to surface water is critical for predicting the impacts of atmospheric deposition and changing land use on water quality in montane catchments. To investigate solute sources and streamflow in the montane Provo River watershed (Utah, USA), we used time‐series 87Sr/86Sr ratios sampled at three sites (Soapstone, Woodland and Hailstone) across a gradient of bedrock types. Soils are influenced by aeolian dust contributions, with distinct 87Sr/86Sr ratios relative to siliciclastic bedrock, providing an opportunity to investigate shallow versus deeper flow paths for controlling water chemistry. At the most upstream site (Soapstone), Sr concentrations averaged ~17 μg/L with minimal dilution during snowmelt suggesting subsurface flow paths dominated streamflow. However, a decrease in 87Sr/86Sr ratios from ~0.717 during baseflow to as low as ~0.713 during snowmelt indicated the activation of shallow flow paths through dust‐derived soils. In contrast, downstream sites receiving water inputs from Sr‐rich carbonate bedrock (Woodland and Hailstone) exhibited strong dilution of Sr from ~120 to 20 μg/L and an increase in 87Sr/86Sr ratios from ~0.7095 to ~0.712 during snowmelt. A three‐component mixing model using 87Sr/86Sr ratios and Sr concentrations at Soapstone showed water inputs were dominated by direct snowmelt and flushed soil water during runoff and groundwater during baseflow. At Woodland and Hailstone, a two‐component mixing model showed that the river was a mixture of groundwater and up to 75% upstream channel water during snowmelt. Our findings highlight the importance of flushed soil water for controlling stream water discharge and chemistry during snowmelt, with the signal from the upstream site propagating downstream in a nested catchment. Further, aeolian dust contributes to the solute chemistry of montane streams with potential impacts on water quality along shallow flow paths. Potential contaminants in these surface soils (e.g., Pb deposition in dust) may have significant impacts on water quality during snowmelt runoff.

Protection Scheme for a Wavelength-Division-Multiplexed Passive Optical Network Based on Reconfigurable Optical Amplifiers

This paper demonstrates a wavelength-division-multiplexed passive optical network (WDM-PON) scheme based on novel reconfigurable optical amplifiers (ROAs). The measured switching characteristics of the ROA3 constructed with a 2 × 2 crossbar optical switch and a four-port reversible optical circulator (OC) and a conventional EDFA can meet the requirements of most network management and surveillance. The self-made four-port reversible OC’s response time is less than 2 ms, and its insertion losses are about 1 dB or less for all the transmission paths and switching states. An optimal design of ROAs is proposed and evaluated for bidirectional optical amplifier protection, in which ROA3 has an EDF length of 7.5 m long with a 1480 nm pump laser and possesses a backward or forward pumping configuration with the corresponding pump power of 200 mW or 50 mW. We verified the scheme’s feasibility through a simulation of WDM-PON systems with 40 downstream and upstream channels. This scheme enables the intelligent protection switching in practical operation scenarios for high-capacity multi-wavelength networks.

Pengaruh Besar Sudut Butterfly Guide terhadap Unjuk Kerja Kincir Air

In this work, the effects of geometry transition of the upstream channel on the performance of an undershot water wheel were investigated. For that purpose, we carried out experiments using an undershot water wheel model with a diameter of Ø=480 mm, the width of l=100 mm, the number of blades of 12, and the radius of blade curvature of R=170 mm, which was installed on a flow channel with the width of 250 mm. The upstream channel was modified by installing flow guides with different entry angles (α=30o, α=45o, and α=60o), and their effects were investigated by measuring the mechanical power of the water wheel and capturing the flow pattern at the upstream of the water wheel, under the flow rates of Q=10 l/s and Q=14 l/s. The experimental results show that the higher the flow rate, the stronger the effects of the flow guides on the performance of the water wheel. Under the considered experimental conditions, the highest performance was achieved for the flow guide with entry angles of α=30o at the flow rate of Q=14 l/s, for which the water wheel produces mechanical power of 22 Watt with an efficiency of 40,37%. It can be observed that the flow guide with the gradual transition (lower entry angle) introduces a more uniform flow pattern that results in a higher water wheel performance, while the flow guide with the sharp transition (higher entry angle) introduces the crossing flow pattern that reduces the performance of the water wheel.

Alteration of the flow distribution at a river bifurcation caused by a system of upstream dams: Case of the Grijalva River basin, Mexico

AbstractMultiple factors control the flow distribution in a river bifurcation. However, one factor that requires further analysis is the effect of upstream reservoirs. Such is the case of the bifurcation of the Mezcalapa River into the Samaria and Carrizal Rivers located in the lowlands of the Grijalva River basin, Mexico. Four dams were commissioned in the upper basin, the first in 1967 and the last in 1987. Since the late 1960s the distribution of the flow at the bifurcation has varied considerably. The flow captured by the Carrizal River between the late 1960s and mid 1980s gradually decreased from 40% to 10%, and later, between the mid 1980s and early 2000s, it increased up to 75%. During the same period, the Samaria River had a reversed pattern. Here, using a two‐dimensional hydro‐morphodynamical model, the impact of an upstream reservoir (that causes homogenization of the flow hydrograph and sediment retention) on bed morphology and flow distribution in a river bifurcation is analyzed. The results indicate that the sediment retention is the factor of largest impact on the flow distribution. The upstream channel incises, and the process propagates to the diffluent with the larger energy gradient developing positive feedback were the erosion increases the hydraulic capacity to capture more flow, resulting in more erosion. The flow homogenization has also an impact. The suppression of peak flows reduces the sediment load capacity in the diffluent with lower energy gradient, generating sedimentation at its entrance and diminishing its hydraulic capacity.

Proposed Improvement on Supply Chain System to Minimize The Bullwhip Effect Phenomenon with Monte Carlo Simulation Approach

PT XYZ is one of the most company which produce welded steel pipe in Indonesia such as longitudinal and spiral pipes. In order to meet consumer’s demand, this company faced with an obstacle namely the distortion of information in supply chain. Distortion of information from downstream to upstream channel causes the difference between the product demand from consumer to PT XYZ and order of raw materials from PT XYZ to the supplier which is called the bullwhip effect. The objective of this research is to calculate the value of bullwhip effect as well as designing improvements to minimize the bullwhip effect. Based on the research results, obtained the index value of bullwhip effect on longitudinal pipe products is 1.06 and the index value of bullwhip effect on spiral pipe products is 0.80. The improvement design to minimize the phenomenon of bullwhip effect is to build an integrated information system for the customer, manufacturer, and supplier. The method that is used to improve the index value of bullwhip effect is Monte Carlo simulation. Monte Carlo simulation is used to obtain the order number of raw materials in order to approach the number of consumer’s demand. After applying the Monte Carlo simulation, obtained the index value of bullwhip effect on longitudinal pipe product is 1.01 and the index value of bullwhip effect on spiral pipe products is 1.00. It can be concluded that the use of Monte Carlo simulation had been optimizing the index value of bullwhip effect amounted to 4.71% for longitudinal pipe products and 25% for spiral pipe products.

Shock propagation channels behind the global economic contagion network. The role of economic sectors and the direction of trade.

Examining the spread of macroeconomic phenomena between countries has become increasingly popular after the 2008 economic crisis, but the recent COVID-19 pandemic rendered this issue much more relevant as it shed more light on the risks arising from strongly interconnected economies. This paper intends to extend previous studies in this line by examining the relationship between trade openness and business cycle synchronization. It extends the scope of previous analyses in three areas. First, we use a Granger-causality approach to identify synchronization. Second, trade is broken down to the sector level and third, we distinguish between upstream and downstream connections. These developments allow for a directed approach in the analysis. We use conditional logit regressions to estimate the effect of trade openness on the probability of shock-transmission. The results presented in this study contribute to the literature in two ways. First, in addition to revealing a positive effect of aggregate two-way trade on shock-contagion, it also points out that this overall effect hides diverse behavior in specific trading sectors as well as upstream and downstream channels. Second, while some sectors are not significant channels of shock-transmission in either directions, upstream channels seem to be important in agriculture while downstream channels dominate machinery and other manufactures. Also, there are sectors (chemicals and related products) trade in which affects shock-transmission negatively.

Learning EPON delay models from data: a machine learning approach

There have been a large number of studies focused on the characterization of the upstream delay in time-division multiplexing passive optical networks (TDM-PONs). However, most of them focus on finding equations for the average delay and ignore other useful metrics like delay percentiles, which are of paramount interest in dimensioning PONs with delay guarantees. This work shows how to learn delay models from data using supervised machine learning (ML) techniques. Essentially, a nonlinear regression ML algorithm is trained with PON simulation data, showing that it can provide accurate equations for such metrics of interest. In particular, we obtain an R 2 score above 80% under Poisson traffic and above 65% under self-similar traffic, and we provide a general equation for any delay percentile in the upstream channel of a PON employing interleaved polling with adaptive cycle time. We further show its applicability in dimensioning Tactile Internet and 5G transport support scenarios.

Exchange rate, industrial linkage, and firm employment

AbstractThis study examines how exchange rate shocks impact firm‐level employment through five transmission channels, namely, the traditional import competition, export revenue, import cost channels, and the innovative upstream and downstream propagation channels. The upstream (downstream) propagation is defined as an indirect channel of the exchange rate shocks that transmits from downstream (upstream) firms via production chains. Augmenting the model of Campa and Goldberg (2001) by incorporating input–output linkage, I develop a theoretical framework to identify the mechanisms of exchange rate effects on firm‐level employment. Using Chinese firm‐level data and the industrial input–output table, this study yields empirical results that confirm the theory robustly. Specifically, the appreciation of exchange rates has large and significantly negative and positive impacts on firms’ employment through the upstream and downstream propagation channels, respectively.

Upstream modes and antidots poison graphene quantum Hall effect

The quantum Hall effect is the seminal example of topological protection, as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. Graphene has made its marks as an exceptional platform to reveal new facets of this remarkable property. However, in conventional Hall bar geometries, topological protection of graphene edge channels is found regrettably less robust than in high mobility semi-conductors. Here, we explore graphene quantum Hall regime at the local scale, using a scanning gate microscope. We reveal the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels, hence triggering topological breakdown. Combined with simulations, our experimental results provide further insights into graphene quantum Hall channels vulnerability. In turn, this may ease future developments towards precise manipulation of topologically protected edge channels hosted in various types of two-dimensional crystals.

Implications of Contract-Bargaining Mechanisms for Coordination and Profit Sharing in a Distribution Channel

The present work models a three-level distribution channel that has a manufacturer, multiple distributors, and multiple retailers under each distributor to analyze channel members’ cooperative, semicooperative, and noncooperative decisions for an arbitrary replenishment cycle other than the first in the infinite time horizon. It uses two sequential bargaining processes: forward contract-bargaining (FCB) and backward contract-bargaining (BCB) to eliminate channel conflict and allocate additional profit among channel members. We successfully implement a hybrid contract mechanism that combines wholesale price discount (WPD) and subsidy on holding cost for channel coordination. The concept of Nash bargaining is applied for additional profit sharing. The proposed hybrid contract can fully coordinate the tree-like supply chain and enrich the entire profit of the supply chain at its best. The manufacturer provides WPD to each distributor separately, and each distributor provides a subsidy to each of its retailers independently. Both the sequential bargaining processes are designed in such a way that an upstream channel member always has the opportunity to account for different reservations for its different downstream members. Although each bargaining process eliminates the channel conflict, finds win-win ranges, and distributes surplus profit, the distributors prefer BCB, whereas the manufacturer and the retailers prefer the FCB. Also, without receiving WPD, the distributors have the ability to coordinate the supply chain and find win-win profits by subsidizing the retailers’ holding costs. A numerical case is presented to explain the findings of the work.

Network analysis and characterization of vulnerability in flood control infrastructure for system-level risk reduction

The number of catastrophic events such as extreme rainfalls and hurricanes has been growing. These events pose a major threat to the life safety and economic prosperity of urban regions. Flood control networks play a pivotal role in mitigating the risk associated with the stormwater generated by extreme rainfalls and hurricanes. The objective of this study is to propose a framework to examine the vulnerability in flood control infrastructure networks. This framework applies graph theory concepts and tools to define a vulnerability index for flood control network components (e.g., channels and rivers). The topological attributes of flood control networks are used to determine the vulnerability index based on structural attributes of flood control networks. First, a flood control network is modeled as a directed graph and storage facilities are incorporated into the network. Second, co-location exposure, upstream channel susceptibility, and discharge redundancy are characterized as important vulnerability attributes of a channel in flood control network. Then, these three characteristics are formulized based on the topological attributes of the network and characteristics of channels. The vulnerability index is then determined based on the three vulnerability characteristics. The proposed vulnerability index can be used to evaluate the impact of different risk reduction policies on flood control network vulnerability and determine the optimal mitigation strategies aiming at flood risk reduction, such as widening vulnerable channels, placement of storage facilities in the network or increasing the redundancy of the network. The framework is implemented on two watersheds in Harris County (Texas, USA) and the results' implications for decision-making in infrastructure management and hazard mitigation planning are discussed. The results highlight the capability of the proposed graph-based framework to inform flood risk reduction through evaluation of the vulnerability of infrastructure networks.

Based on a biological particle model to predict the trace behavior of fish

AbstractA biological particle model is used to predict the upward trajectory of fish under a dam, the biological particle model refers to a fish as a particle and considers the flow rate, velocity gradient and turbulent energy of the fish, as a condition of retrospective behaviour, a control equation is used to simplify the fish's retroactive behaviour and establish a model programmed in MATLAB to develop a fish traceability prediction program. According to the program, the upward trajectory of the fish under the dam is predicted, there are three types of up-tracking channels under the dam according to the average widths of the up-tracking channels along the right bank of the channel, along the middle of the channel, and along the left bank of the channel and the average widths are 10, 14 and 7 m, respectively. The three existing fish import locations in the fishway project are evaluated, and optimization recommendations are provided, it is recommended to add a fishway inlet along the right bank of the upstream channel. In addition, this paper provides a feasible technical methodology by which a biological particle model can be used to predict the upward trajectory of fish in similar fishway projects.

Climate‐Change Controls on River Delta Avulsion Location and Frequency

AbstractCoastal rivers that build deltas undergo repeated avulsion events—that is, abrupt changes in river course—which we need to understand to predict land building and flood hazards in coastal landscapes. Climate change can impact water discharge, flood frequency, sediment supply, and sea level, all of which could impact avulsion location and frequency. Here we present results from quasi‐2D morphodynamic simulations of repeated delta‐lobe construction and avulsion to explore how avulsion location and frequency are affected by changes in relative sea level, sediment supply, and flood regime. Model results indicate that relative sea‐level rise drives more frequent avulsions that occur at a distance from the shoreline set by backwater hydrodynamics. Reducing the sediment supply relative to transport capacity has little impact on deltaic avulsions, because, despite incision in the upstream trunk channel, deltas can still aggrade as a result of progradation. However, increasing the sediment supply relative to transport capacity can shift avulsions upstream of the backwater zone because aggradation in the trunk channel outpaces progradation‐induced delta aggradation. Increasing frequency of overbank floods causes less frequent avulsions because floods scour the riverbed within the backwater zone, slowing net aggradation rates. Results provide a framework to assess upstream and downstream controls on avulsion patterns over glacial‐interglacial cycles, and the impact of land use and anthropogenic climate change on deltas.

Monitoring Turbidity in San Francisco Estuary and Sacramento-San Joaquin Delta Using Satellite Remote Sensing.

This study utilizes satellite data to investigate water quality conditions in the San Francisco Estuary and its upstream delta, the Sacramento–San Joaquin River Delta. To do this, this study derives turbidity from the European Space Agency satellite Sentinel‐2 acquired from September 2015 to June 2019 and conducts a rigorous validation with in situ measurements of turbidity from optical sensors at continuous monitoring stations. This validation includes 965 matchup comparisons between satellite and in situ sensor data across 22 stations, yielding R 2 = 0.63 and 0.75 for Nephelometric Turbidity Unit and Formazin Nephelometric Unit (FNU) stations, respectively. This study then applies remote sensing to evaluate patterns in turbidity during the Suisun Marsh Salinity Control Gates Action (“Gates action”), a pilot study designed to increase habitat access and quality for the endangered Delta Smelt. The basic strategy was to direct more freshwater into Suisun Marsh, creating more low salinity habitat that would then have higher (and more suitable) turbidity than upstream river channels. For all seven acquisitions considered from June 29 to September 27, 2018, turbidity conditions in Bays and Sloughs subregions were consistently higher (and more suitable) (26–47 FNU) than what was observed in the upstream River region (13–25 FNU). This overall pattern was observed when comparing images acquired during similar tidal stages and heights.