The technique of Farmer Managed Natural Regeneration (FMNR) is being promoted as a cost-effective approach for restoring degraded arable dry lands. Its effectiveness has been observed in many countries across the glob...The technique of Farmer Managed Natural Regeneration (FMNR) is being promoted as a cost-effective approach for restoring degraded arable dry lands. Its effectiveness has been observed in many countries across the globe, where it is a traditional practice, and is now being encouraged across the African continent. This study aimed to evaluate the impact of FMNR on floristic Composition, Vegetation Structure, and Regeneration Status of woody Plant Species in the severely degraded Central Rift, Kenya. The study systematically assessed how FMNR influenced species composition, vegetation structure and regeneration status from two sample plots involved in FMNR practices. Transect lines and quadrats methods were utilized to collect data, specifically regarding the floristic composition, vegetation structure, and regeneration status of woody plant species. Quadrats and sub-quadrats of varying sizes (10 m by 10 m, 5 m by 5 m, and 1 m by 1 m) were nested along the transect lines for data collection. Furthermore, measurements of tree growth and development, including root collar diameter, diameter at breast height (D<sub>130</sub>) and heights within the study blocks, were taken. The data was then analyzed using R-software. Results showed a marked progressive increase in numbers of trees, saplings, seedlings, shrubs and herbs in all FMNR sites and reductions in all non-FMNR sites. The study advocates for widespread promotion of the FMNR practice both as an environmental conservation and restoration strategy.展开更多
Background:More than a decade of fire suppression has changed the structure of fire-adapted shrubland ecosystems in Spain’s National Parks,which are now at extreme risk of uncontrolled wildfires.Prescribed burning ca...Background:More than a decade of fire suppression has changed the structure of fire-adapted shrubland ecosystems in Spain’s National Parks,which are now at extreme risk of uncontrolled wildfires.Prescribed burning can mitigate the risk of wildfires by reducing the fuel load but prescribed burning may also alter the soil properties and reduce microbial and fungal activity,causing changes in the availability of nutrients deep in the soil layer.Although fungal communities are a vital part of post-fire restoration,some fire effects remain unclear.To examine the short-term effects of prescribed burning on soil fungal communities in Doñana Biological Reserve(SW Spain),we collected soil samples pre-burn and 1 day,6 and 12 months post-burn from burned plots to perform physicochemical and metabarcode DNA analyses.Results:Prescribed burning had no significant effect on the total fungal operational taxonomic unit richness and abundance.However,changes in soil pH,nitrogen and potassium content post-burn affected fungal community composition.Small non-significant changes in pH and phosphorous affected the composition of ectomycorrhizal fungi.Conclusions:The ectomycorrhizal fungal community appears to be resilient to the effects of low-to moderate-intensity fires and saprotrophic taxa may benefit from this kind of fire.This finding revealed that prescribed burning is a potentially valuable management tool for reducing fire hazards in shrublands that has little effect on the total richness and abundance of fungal communities.展开更多
By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, construc...By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, constructs a VMI mathematics model, and analyzes the influence of VMI on inventory cost and channel profit. Finally, a special case is studied to verify that VMI is an effective supply chain strategy that can not only increase channel profit of supplier and customer but also improve full channel coordination, thereby reducing the bullwhip effect.展开更多
This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple ...This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple exponentially weighted moving average. It also examines a vendor managed inventory (VMI) program to determine how it can help alleviate such negative effects, and gives the theoretical proofs and numerical illustrations. The results show that the effects with VMI are better than the effect without VMI in demand forecasting and safety stock levels, etc.展开更多
During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas...During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.展开更多
In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consoli...In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.展开更多
The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, havi...The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, having initial stock and having stock-out cost. With the further analysis of the mode, VMI is found to increase profits of the buyer in the short-term motivation. But VMI will reduce profits of the supplier under the matching condition. And in the short-term motivation, VMI will increase the purchase price to compensate the transfer cost of the supplier. As a result, the foundation of theory is provided to implement VMI in the supply chain, and have some definituded project significance.展开更多
The aim of this research was to evaluate the amount of woody debris (m3/ha) on the forest floor and the associated wood-colonizing fungi. The study was performed in the Taborz region, known for its Scots pine provenan...The aim of this research was to evaluate the amount of woody debris (m3/ha) on the forest floor and the associated wood-colonizing fungi. The study was performed in the Taborz region, known for its Scots pine provenance experiments, against the background of a recently launched Polish legislation to protect the biodiversity on the forest floor in managed (harvested) stands. We investigated a managed stand (136-years-old) and the reserve stand ‘Sosna Taborska’(261-years-old). In the reserve stand, the mean volume of woody debris was six times higher than in the managed forests, i.e. 65 versus 11 m3/ha. In addition, in the reserve stand, the number of fungi taxa colonizing the dead wood was larger than in the managed stands, with a higher number of fruitbodies. Total fungal richness was higher in the reserve than in the managed stand, i.e. 28 versus 12 species. The dominant taxa at both sites were Fomitopsis pinicola and Fomes The aim of this research was to evaluate the amount of woody debris (m^3/ha) on the forest floor and the associated wood-colonizing fungi. The study was performed in the Taborz region, known for its Scots pine provenance experiments, against the background of a recently launched Polish legislation to protect the biodiversity on the forest floor in managed (harvested) stands. We investigated a managed stand (136-years-old) and the reserve stand ‘Sosna Taborska’(261-years-old). In the reserve stand, the mean volume of woody debris was six times higher than in the managed forests, i.e. 65 versus 11 m^3/ha. In addition, in the reserve stand, the number of fungi taxa colonizing the dead wood was larger than in the managed stands, with a higher number of fruitbodies. Total fungal richness was higher in the reserve than in the managed stand, i.e. 28 versus 12 species. The dominant taxa at both sites were Fomitopsis pinicola and Fomes fomentarius, although some taxa were only found in the reserve (e.g., Stereum hirsutum). The volume of woody debris as well as the diversity of fungi in the managed stand were lower than in the reserve, albeit greater than in other Scots pine stands in Poland. These results testify to the gains in biodiversity yielded by the management conservation management approach at the reserve stand.展开更多
The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilli...The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilling technology.If we can solve these problems,the economics of drilling the wells will improve,thus enabling the industry to drill wells that were previously uneconomical.Managed pressure drilling techniques,at one time,having展开更多
This research investigates the impact of managed health care on academic medical centers in the United States. Academic medical centers hold a unique position in the U. S. health care system through their missions of ...This research investigates the impact of managed health care on academic medical centers in the United States. Academic medical centers hold a unique position in the U. S. health care system through their missions of conducting cutting-edge biomedical researeh, pursuing clinical and technological innovations, Providing state-of-the-art medical care and producing highly qUalified health professionals. However, policies to control costs through the use of managed care and limiting resources are detrimental to academic medical centers and impede the advancement of medical sciTo survive the threats of managed care in the health care environment, acadendc medical centers must rely on their upper level managers to derive successful strategies. The methods used in this study include qualitative approaches in the form of key informants and case studies. In addition, a survey questionnaire was sent to 1h8 CEOs in all the academic medical centers in the U. S. The findings revealed that managers who perform the liaison, monitor, entrepreneur and resource allocator roles are crucial to ensure the survival of academic medical centers, so that academic medical centers can continue their missions to serve the general public and promote their well-being.展开更多
This study explored the hydrological and economic feasibility of managed aquifer recharge(MAR) using tertiary treated wastewater(TWW) to mitigate salinity in the coastal aquifer of Jamma, Oman. A steady-state groundwa...This study explored the hydrological and economic feasibility of managed aquifer recharge(MAR) using tertiary treated wastewater(TWW) to mitigate salinity in the coastal aquifer of Jamma, Oman. A steady-state groundwater flow and transport model, using MODFLOW software, was developed and calibrated. Different managerial scenarios were simulated and the results reveal that the Jamma aquifer will be further deteriorated in the next 20 a if it remains unmanaged. The groundwater table will decline further by more than 3 m on average; and the iso-concentration salinity line of 1500 mg/L will advance 2.7 km inland, which will severely affect the farming activities in the area. However, MAR using TWW when integrated with the management of groundwater abstraction(e.g., using modern irrigation systems to reduce the abstraction rate) becomes hydrologically feasible to augment the aquifer storage and control seawater intrusion, and hence improves the farming activities. The results indicate that:(1) injecting TWW in the vicinity of irrigation wells(Scenario A2);(2) investing in smart water meters and online control of pumping from the wells to reduce the abstraction rate by 25%(Scenario B); and(3) a combination of both(Scenario B2) are feasible scenarios with positive net present values. Recharge in upstream areas is found not economically feasible because of the very high investment cost of the installation of pipes to transport the TWW over a distance of 12.5 km. Because of securing funds are challenging, Scenario B would be the best option and the second-best option is Scenario A2. Scenario B2 has the lowest net benefit investment ratio and is very attractive because it entails integrated demand and supply management of groundwater. It is required to reduce pumping and to invest in injecting TWW to improve groundwater quality in the vicinity of irrigation wells and to form a hydrological barrier to control seawater intrusion in the long run.展开更多
We compared the dead wood （DW） conditions of Chesh- meh-sar forest and Sardab forest with different management history, including reserve forest and harvested forest. The First forest took 100% inventory from all th...We compared the dead wood （DW） conditions of Chesh- meh-sar forest and Sardab forest with different management history, including reserve forest and harvested forest. The First forest took 100% inventory from all the available DW. Also dead trees were compared in terms of species, shape, location and quality of fracture in both forests. Volumes of dead wood in Cheshmeh-sar and Sardab forests were 207.47 and 142.74 m3, respectively. Due to this significant difference, impact on the management level was determined. In Cheshmeh-sar forest, 42% of dead trees were standing and 58% were fallen type while in Sardab forest 38.6% were standing and 61.4% fallen. But the difference was not statis- tically significant l^etween them （p = 0.0587）. In terms of quality, dead trees of hard, soft and hollow had the highest frequency, respectively. However, 71.5% of DW was seen as hard dead in Cheshmeh-sar forest while hard dead trees in Sardab forests were 54.2%. Soft quality degree of dead trees which formed in Cheshmeh-sar and Sardab forest were calcu- lated as 26.6% and 43.4% respectively. Also 30% of the dead trees of Sardab forest were eradicated while in Cheshmeh-sar this amount was reduced to 12%. Due to this significant difference （（P=0/018）, it is concluded that the type of management and human interference are affecting the quality of dead trees and makes us to think the human in- terferences could effect on the ecosystem of touched forests.展开更多
Until the early 1990s the Azraq basin in Jordan was covered by a huge wetland in the central parts representing a source of fresh water for all purposes. The presence of such wetland in the desert created a natural pa...Until the early 1990s the Azraq basin in Jordan was covered by a huge wetland in the central parts representing a source of fresh water for all purposes. The presence of such wetland in the desert created a natural pathway for migratory birds. Man made and natural impacts caused severe depletion of this basin and the oasis disappeared in the early 1990s. Under a GIS environment MAR layers were prepared for the Azraq basin. MAR mapping showed a very high and high potentials over 20.55% and 61.63% of the total basin area respectively;while the low potential areas represent only 4.03% of the total area.展开更多
The article deals with the feasibility of using the recent geological formations in the eastern Jordan Valley for water storage through artificial recharge due to water scarcity and water needs in this area. Water sto...The article deals with the feasibility of using the recent geological formations in the eastern Jordan Valley for water storage through artificial recharge due to water scarcity and water needs in this area. Water storage in surface reservoirs in arid and semi-arid areas is afflicted with a variety of issues such as high evaporation, eutrophication processes and exposure to contamination and accidents. Dams to capture all rare-event floods are, generally, big and expensive structures. Artificially recharging aquifers and storing the water in the underground offer a competing alternative. In this study, hydrogeological, geological, geophysical and hydrochemical investigations were carried out to study the potentials of the eastern side of the Lower Jordan Valley for artificial recharge. The results reveal that relatively extended areas on the eastern side of the Lower Jordan Valley have the potential to accommodate large amounts of recharge water and that the impacts of artificially storing the water in aquifers are to be judged very positive compared to surface storage, especially when the amounts of available recharge water can quantitatively be accommodated in recharge facilities. In addition, the study shows, the advantages of underground water storage compared to surface storage in dams. The potential storage capacities in the different parts of the Lower Jordan Valley are quantified based on rechargeable aquifer volumes and porosities. The potential uses of the recharged water are also elaborated on depending on recharge and aquifer water qualities.展开更多
Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not bee...Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.展开更多
Groundwater is of fundamental significance for human society,especially in semi-arid areas in China.However,due to the fast social and economic development,China has been suffering from the shortage of water resource....Groundwater is of fundamental significance for human society,especially in semi-arid areas in China.However,due to the fast social and economic development,China has been suffering from the shortage of water resource.In this situation,managed aquifer recharge(MAR)was considered to be an effective measure for the sustainable management of groundwater resources.Since 1960 s,China successfully implemented many MAR schemes for different purposes such as restoration of groundwater tables,prevention of seawater intrusion,increasing urban water supplies and controlling land subsidence.From those successful experiences China developed a scientific and applicable system to implement MAR project.However,there were still many challenges in this field,for example,treated waste water had been barely used for recharge.The present review summarized the achievements in MAR applications in China as well as the associated challenges within the past 55 years before the year 2016.展开更多
The dispersion-managed soliton (DMS) transmission model of dispersion-managed systems is established,and the intrachannel DMS interactions equation is obtained.The impact of soliton interactions on DMS systems are num...The dispersion-managed soliton (DMS) transmission model of dispersion-managed systems is established,and the intrachannel DMS interactions equation is obtained.The impact of soliton interactions on DMS systems are numerically investigated.Finally,the relationships of the collision length changing with map strength are revealed.展开更多
文摘The technique of Farmer Managed Natural Regeneration (FMNR) is being promoted as a cost-effective approach for restoring degraded arable dry lands. Its effectiveness has been observed in many countries across the globe, where it is a traditional practice, and is now being encouraged across the African continent. This study aimed to evaluate the impact of FMNR on floristic Composition, Vegetation Structure, and Regeneration Status of woody Plant Species in the severely degraded Central Rift, Kenya. The study systematically assessed how FMNR influenced species composition, vegetation structure and regeneration status from two sample plots involved in FMNR practices. Transect lines and quadrats methods were utilized to collect data, specifically regarding the floristic composition, vegetation structure, and regeneration status of woody plant species. Quadrats and sub-quadrats of varying sizes (10 m by 10 m, 5 m by 5 m, and 1 m by 1 m) were nested along the transect lines for data collection. Furthermore, measurements of tree growth and development, including root collar diameter, diameter at breast height (D<sub>130</sub>) and heights within the study blocks, were taken. The data was then analyzed using R-software. Results showed a marked progressive increase in numbers of trees, saplings, seedlings, shrubs and herbs in all FMNR sites and reductions in all non-FMNR sites. The study advocates for widespread promotion of the FMNR practice both as an environmental conservation and restoration strategy.
基金Spanish R&D projects MYCOINFOR(Mycosilviculture Applied to Forest Fire Prevention in Mediterranean SystemsPID2019-105188RB-I00)+4 种基金VIS4FIRE(Comprehensive vulnerability of forest systems to fire:implications for forest management toolsRTA2017-00042-C05-01)Interreg-POCTEP CILIFO(Iberian Centre for Research and Forest Firefighting0753-CILIFO-5-E)financed by European Social Fund“NextGenerationEU”through a grant“Margarita Salas”awarded to Juncal Espinosa into the project GFIRE。
文摘Background:More than a decade of fire suppression has changed the structure of fire-adapted shrubland ecosystems in Spain’s National Parks,which are now at extreme risk of uncontrolled wildfires.Prescribed burning can mitigate the risk of wildfires by reducing the fuel load but prescribed burning may also alter the soil properties and reduce microbial and fungal activity,causing changes in the availability of nutrients deep in the soil layer.Although fungal communities are a vital part of post-fire restoration,some fire effects remain unclear.To examine the short-term effects of prescribed burning on soil fungal communities in Doñana Biological Reserve(SW Spain),we collected soil samples pre-burn and 1 day,6 and 12 months post-burn from burned plots to perform physicochemical and metabarcode DNA analyses.Results:Prescribed burning had no significant effect on the total fungal operational taxonomic unit richness and abundance.However,changes in soil pH,nitrogen and potassium content post-burn affected fungal community composition.Small non-significant changes in pH and phosphorous affected the composition of ectomycorrhizal fungi.Conclusions:The ectomycorrhizal fungal community appears to be resilient to the effects of low-to moderate-intensity fires and saprotrophic taxa may benefit from this kind of fire.This finding revealed that prescribed burning is a potentially valuable management tool for reducing fire hazards in shrublands that has little effect on the total richness and abundance of fungal communities.
文摘By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, constructs a VMI mathematics model, and analyzes the influence of VMI on inventory cost and channel profit. Finally, a special case is studied to verify that VMI is an effective supply chain strategy that can not only increase channel profit of supplier and customer but also improve full channel coordination, thereby reducing the bullwhip effect.
文摘This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple exponentially weighted moving average. It also examines a vendor managed inventory (VMI) program to determine how it can help alleviate such negative effects, and gives the theoretical proofs and numerical illustrations. The results show that the effects with VMI are better than the effect without VMI in demand forecasting and safety stock levels, etc.
基金supported by the Youth Program of National Natural Science Foundation of China(Grant No.52104012)the Key Program of the National Natural Science Foundation of China(Grant No.51734010)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M693494)Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKBH011)the Key Natural Science Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region(Grant No.XJEDU2021I028)。
文摘During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.
基金The National Key Technology R&D Program of China during the 11 th Five-Year Plan Period(No.2006BAH02A06)
文摘In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.
文摘The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, having initial stock and having stock-out cost. With the further analysis of the mode, VMI is found to increase profits of the buyer in the short-term motivation. But VMI will reduce profits of the supplier under the matching condition. And in the short-term motivation, VMI will increase the purchase price to compensate the transfer cost of the supplier. As a result, the foundation of theory is provided to implement VMI in the supply chain, and have some definituded project significance.
基金supported by statutory funds No.15/20.610.028-300 from the Faculty of Environmental Management and Agriculture of the University of Warmia and Mazury in Olsztyn
文摘The aim of this research was to evaluate the amount of woody debris (m3/ha) on the forest floor and the associated wood-colonizing fungi. The study was performed in the Taborz region, known for its Scots pine provenance experiments, against the background of a recently launched Polish legislation to protect the biodiversity on the forest floor in managed (harvested) stands. We investigated a managed stand (136-years-old) and the reserve stand ‘Sosna Taborska’(261-years-old). In the reserve stand, the mean volume of woody debris was six times higher than in the managed forests, i.e. 65 versus 11 m3/ha. In addition, in the reserve stand, the number of fungi taxa colonizing the dead wood was larger than in the managed stands, with a higher number of fruitbodies. Total fungal richness was higher in the reserve than in the managed stand, i.e. 28 versus 12 species. The dominant taxa at both sites were Fomitopsis pinicola and Fomes The aim of this research was to evaluate the amount of woody debris (m^3/ha) on the forest floor and the associated wood-colonizing fungi. The study was performed in the Taborz region, known for its Scots pine provenance experiments, against the background of a recently launched Polish legislation to protect the biodiversity on the forest floor in managed (harvested) stands. We investigated a managed stand (136-years-old) and the reserve stand ‘Sosna Taborska’(261-years-old). In the reserve stand, the mean volume of woody debris was six times higher than in the managed forests, i.e. 65 versus 11 m^3/ha. In addition, in the reserve stand, the number of fungi taxa colonizing the dead wood was larger than in the managed stands, with a higher number of fruitbodies. Total fungal richness was higher in the reserve than in the managed stand, i.e. 28 versus 12 species. The dominant taxa at both sites were Fomitopsis pinicola and Fomes fomentarius, although some taxa were only found in the reserve (e.g., Stereum hirsutum). The volume of woody debris as well as the diversity of fungi in the managed stand were lower than in the reserve, albeit greater than in other Scots pine stands in Poland. These results testify to the gains in biodiversity yielded by the management conservation management approach at the reserve stand.
文摘The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilling technology.If we can solve these problems,the economics of drilling the wells will improve,thus enabling the industry to drill wells that were previously uneconomical.Managed pressure drilling techniques,at one time,having
文摘This research investigates the impact of managed health care on academic medical centers in the United States. Academic medical centers hold a unique position in the U. S. health care system through their missions of conducting cutting-edge biomedical researeh, pursuing clinical and technological innovations, Providing state-of-the-art medical care and producing highly qUalified health professionals. However, policies to control costs through the use of managed care and limiting resources are detrimental to academic medical centers and impede the advancement of medical sciTo survive the threats of managed care in the health care environment, acadendc medical centers must rely on their upper level managers to derive successful strategies. The methods used in this study include qualitative approaches in the form of key informants and case studies. In addition, a survey questionnaire was sent to 1h8 CEOs in all the academic medical centers in the U. S. The findings revealed that managers who perform the liaison, monitor, entrepreneur and resource allocator roles are crucial to ensure the survival of academic medical centers, so that academic medical centers can continue their missions to serve the general public and promote their well-being.
基金supported by the USAID (United States Agency for International Development)-FABRI (Further Advancing the Blue Revolution Initiative) and the MENA NWC (Middle East and North Africa Network of Water Centers of Excellence) (1001626-104)the support of Sultan Qaboos University+1 种基金the Ministry of Regional MunicipalitiesWater Resources in Oman
文摘This study explored the hydrological and economic feasibility of managed aquifer recharge(MAR) using tertiary treated wastewater(TWW) to mitigate salinity in the coastal aquifer of Jamma, Oman. A steady-state groundwater flow and transport model, using MODFLOW software, was developed and calibrated. Different managerial scenarios were simulated and the results reveal that the Jamma aquifer will be further deteriorated in the next 20 a if it remains unmanaged. The groundwater table will decline further by more than 3 m on average; and the iso-concentration salinity line of 1500 mg/L will advance 2.7 km inland, which will severely affect the farming activities in the area. However, MAR using TWW when integrated with the management of groundwater abstraction(e.g., using modern irrigation systems to reduce the abstraction rate) becomes hydrologically feasible to augment the aquifer storage and control seawater intrusion, and hence improves the farming activities. The results indicate that:(1) injecting TWW in the vicinity of irrigation wells(Scenario A2);(2) investing in smart water meters and online control of pumping from the wells to reduce the abstraction rate by 25%(Scenario B); and(3) a combination of both(Scenario B2) are feasible scenarios with positive net present values. Recharge in upstream areas is found not economically feasible because of the very high investment cost of the installation of pipes to transport the TWW over a distance of 12.5 km. Because of securing funds are challenging, Scenario B would be the best option and the second-best option is Scenario A2. Scenario B2 has the lowest net benefit investment ratio and is very attractive because it entails integrated demand and supply management of groundwater. It is required to reduce pumping and to invest in injecting TWW to improve groundwater quality in the vicinity of irrigation wells and to form a hydrological barrier to control seawater intrusion in the long run.
文摘We compared the dead wood （DW） conditions of Chesh- meh-sar forest and Sardab forest with different management history, including reserve forest and harvested forest. The First forest took 100% inventory from all the available DW. Also dead trees were compared in terms of species, shape, location and quality of fracture in both forests. Volumes of dead wood in Cheshmeh-sar and Sardab forests were 207.47 and 142.74 m3, respectively. Due to this significant difference, impact on the management level was determined. In Cheshmeh-sar forest, 42% of dead trees were standing and 58% were fallen type while in Sardab forest 38.6% were standing and 61.4% fallen. But the difference was not statis- tically significant l^etween them （p = 0.0587）. In terms of quality, dead trees of hard, soft and hollow had the highest frequency, respectively. However, 71.5% of DW was seen as hard dead in Cheshmeh-sar forest while hard dead trees in Sardab forests were 54.2%. Soft quality degree of dead trees which formed in Cheshmeh-sar and Sardab forest were calcu- lated as 26.6% and 43.4% respectively. Also 30% of the dead trees of Sardab forest were eradicated while in Cheshmeh-sar this amount was reduced to 12%. Due to this significant difference （（P=0/018）, it is concluded that the type of management and human interference are affecting the quality of dead trees and makes us to think the human in- terferences could effect on the ecosystem of touched forests.
文摘Until the early 1990s the Azraq basin in Jordan was covered by a huge wetland in the central parts representing a source of fresh water for all purposes. The presence of such wetland in the desert created a natural pathway for migratory birds. Man made and natural impacts caused severe depletion of this basin and the oasis disappeared in the early 1990s. Under a GIS environment MAR layers were prepared for the Azraq basin. MAR mapping showed a very high and high potentials over 20.55% and 61.63% of the total basin area respectively;while the low potential areas represent only 4.03% of the total area.
文摘The article deals with the feasibility of using the recent geological formations in the eastern Jordan Valley for water storage through artificial recharge due to water scarcity and water needs in this area. Water storage in surface reservoirs in arid and semi-arid areas is afflicted with a variety of issues such as high evaporation, eutrophication processes and exposure to contamination and accidents. Dams to capture all rare-event floods are, generally, big and expensive structures. Artificially recharging aquifers and storing the water in the underground offer a competing alternative. In this study, hydrogeological, geological, geophysical and hydrochemical investigations were carried out to study the potentials of the eastern side of the Lower Jordan Valley for artificial recharge. The results reveal that relatively extended areas on the eastern side of the Lower Jordan Valley have the potential to accommodate large amounts of recharge water and that the impacts of artificially storing the water in aquifers are to be judged very positive compared to surface storage, especially when the amounts of available recharge water can quantitatively be accommodated in recharge facilities. In addition, the study shows, the advantages of underground water storage compared to surface storage in dams. The potential storage capacities in the different parts of the Lower Jordan Valley are quantified based on rechargeable aquifer volumes and porosities. The potential uses of the recharged water are also elaborated on depending on recharge and aquifer water qualities.
文摘Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.
基金supported by German Federal Ministry of Education and Research(BMBF),project number 01LN1311A。
文摘Groundwater is of fundamental significance for human society,especially in semi-arid areas in China.However,due to the fast social and economic development,China has been suffering from the shortage of water resource.In this situation,managed aquifer recharge(MAR)was considered to be an effective measure for the sustainable management of groundwater resources.Since 1960 s,China successfully implemented many MAR schemes for different purposes such as restoration of groundwater tables,prevention of seawater intrusion,increasing urban water supplies and controlling land subsidence.From those successful experiences China developed a scientific and applicable system to implement MAR project.However,there were still many challenges in this field,for example,treated waste water had been barely used for recharge.The present review summarized the achievements in MAR applications in China as well as the associated challenges within the past 55 years before the year 2016.
文摘The dispersion-managed soliton (DMS) transmission model of dispersion-managed systems is established,and the intrachannel DMS interactions equation is obtained.The impact of soliton interactions on DMS systems are numerically investigated.Finally,the relationships of the collision length changing with map strength are revealed.
