In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle...In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle of 5M1E, systematically sort out and identify all kinds of change points in the assembly process of mining machinery products, output the list of change points and formulate corresponding control measures to standardize them. When the change points are opened, what measures should be taken within the specified time, and how to track the effective implementation of the measures, so as to ensure the smooth progress of production and the effective control of assembly quality.展开更多
The handover speed is always vital for the further development of Wireless Local Area Network (WLAN), which is enjoying a fast growth. Based on the handover technology specified in IEEE 802.11 WLAN, Manageable Fast Ha...The handover speed is always vital for the further development of Wireless Local Area Network (WLAN), which is enjoying a fast growth. Based on the handover technology specified in IEEE 802.11 WLAN, Manageable Fast Handover (MFHO) mechanism is proposed to speed up handover at the Access Point (AP), meet handover demands of services with different Quality of Service (QoS), and ensure service continuity. Adopting a handover policy named 'Make-before-break', this mechanism enables wireless APs to control and manage handover between two stations based on improving Inter-Access Point Protocol (IAPP). Tests have been carried out to compare functions and performance of MFHO and IAPP-based handover technology. The test results prove that MFHO provides a higher successful handover ratio and better handover performance than IAPP-based handover technology.展开更多
Small-scale fisheries,particularly those targeting small pelagic fish,are a vital sector in Liberia,providing essential food for the local population and generating income for livelihoods.Sardinella maderensis,predomi...Small-scale fisheries,particularly those targeting small pelagic fish,are a vital sector in Liberia,providing essential food for the local population and generating income for livelihoods.Sardinella maderensis,predominantly caught by motorized canoes using gill nets and seine nets,is the primary species in these fisheries.To establish management target reference points for the S.maderensis fishery,this study applied the Schaefer production model to aggregated and disaggregated catch and effort data collected by Liberia's National Fisheries and Aquaculture Authority(NaFAA)from 2018 to 2022.The findings indicate that,in both the aggregated and disaggregated models,the current(2022)fishing effort exceeds the MEY level,leading to diminishing economic returns and approaching economic overfishing thresholds.The economic reference points,MEY and EMEY,were estimated to be 3%and 19%lower in the aggregated model,and 30%and 44%lower in the disaggregated model,compared to the current(2022)catch and relative fishing effort.This situation arises when the cost of fishing exceeds the price of fish,driven by inefficient and ineffective fishing boats,which leads to high unit costs of effort compared to unit revenue.To fully realize the potential of the S.maderensis fishery,this study recommends a combination of input and output control management strategies,the adoption of more efficient fishing technologies,and the provision of alternative livelihoods for coastal communities.展开更多
The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently,...The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals （RTLM） such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature （here defined as lower than O^C） has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceableroles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modem advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next- generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.展开更多
In the Internet of Things（IoT）, various battery-powered wireless devices are connected to collect and exchange data, and typical traffic is periodic and heterogeneous. Polling with power management is a very promisi...In the Internet of Things（IoT）, various battery-powered wireless devices are connected to collect and exchange data, and typical traffic is periodic and heterogeneous. Polling with power management is a very promising technique that can be used for communication among these devices in the IoT. In this paper, we propose a novel and scalable model to study the delay and the power consumption performance for polling schemes with power management under heterogeneous settings（particularly the heterogeneous sleeping interval）. In our model,by introducing the concept of virtual polling interval, we successfully convert the considered energy-efficient polling scheme into an equivalent purely-limited vacation system. Thus, we can easily evaluate the mean and variance of the delay and the power consumption by applying existing queueing formulae, without developing a new theoretical model as required in previous works. Extensive simulations show that our analytical results are very accurate for both homogeneous and heterogeneous settings.展开更多
文摘In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle of 5M1E, systematically sort out and identify all kinds of change points in the assembly process of mining machinery products, output the list of change points and formulate corresponding control measures to standardize them. When the change points are opened, what measures should be taken within the specified time, and how to track the effective implementation of the measures, so as to ensure the smooth progress of production and the effective control of assembly quality.
文摘The handover speed is always vital for the further development of Wireless Local Area Network (WLAN), which is enjoying a fast growth. Based on the handover technology specified in IEEE 802.11 WLAN, Manageable Fast Handover (MFHO) mechanism is proposed to speed up handover at the Access Point (AP), meet handover demands of services with different Quality of Service (QoS), and ensure service continuity. Adopting a handover policy named 'Make-before-break', this mechanism enables wireless APs to control and manage handover between two stations based on improving Inter-Access Point Protocol (IAPP). Tests have been carried out to compare functions and performance of MFHO and IAPP-based handover technology. The test results prove that MFHO provides a higher successful handover ratio and better handover performance than IAPP-based handover technology.
文摘Small-scale fisheries,particularly those targeting small pelagic fish,are a vital sector in Liberia,providing essential food for the local population and generating income for livelihoods.Sardinella maderensis,predominantly caught by motorized canoes using gill nets and seine nets,is the primary species in these fisheries.To establish management target reference points for the S.maderensis fishery,this study applied the Schaefer production model to aggregated and disaggregated catch and effort data collected by Liberia's National Fisheries and Aquaculture Authority(NaFAA)from 2018 to 2022.The findings indicate that,in both the aggregated and disaggregated models,the current(2022)fishing effort exceeds the MEY level,leading to diminishing economic returns and approaching economic overfishing thresholds.The economic reference points,MEY and EMEY,were estimated to be 3%and 19%lower in the aggregated model,and 30%and 44%lower in the disaggregated model,compared to the current(2022)catch and relative fishing effort.This situation arises when the cost of fishing exceeds the price of fish,driven by inefficient and ineffective fishing boats,which leads to high unit costs of effort compared to unit revenue.To fully realize the potential of the S.maderensis fishery,this study recommends a combination of input and output control management strategies,the adoption of more efficient fishing technologies,and the provision of alternative livelihoods for coastal communities.
文摘The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals （RTLM） such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature （here defined as lower than O^C） has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceableroles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modem advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next- generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.
基金supported by Macao FDCT-MOST grant 001/2015/AMJ, Macao FDCT grants 013/2014/A1 and 005/2016/A1the National Natural Science Foundation of China (Nos. 61373027 and 61672321)the Natural Science Foundation of Shandong Province (No. ZR2012FM023)
文摘In the Internet of Things（IoT）, various battery-powered wireless devices are connected to collect and exchange data, and typical traffic is periodic and heterogeneous. Polling with power management is a very promising technique that can be used for communication among these devices in the IoT. In this paper, we propose a novel and scalable model to study the delay and the power consumption performance for polling schemes with power management under heterogeneous settings（particularly the heterogeneous sleeping interval）. In our model,by introducing the concept of virtual polling interval, we successfully convert the considered energy-efficient polling scheme into an equivalent purely-limited vacation system. Thus, we can easily evaluate the mean and variance of the delay and the power consumption by applying existing queueing formulae, without developing a new theoretical model as required in previous works. Extensive simulations show that our analytical results are very accurate for both homogeneous and heterogeneous settings.
