In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave co...In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave compensation system,the lifting pipe simulator,the buffer simulator and the water pool.The tests ofmining ship motion simulator show that it is able to perform under the predetermined attitude path smoothly and can meet the requirements of themining ship motions.The heave compensation effect is more than 60% under random wave and the goal is set to be 50%.The model test results indicate that this heave compensation system is effective and feasible.展开更多
Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by th...Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.展开更多
This paper reports the results of experimental research the longitudinal stiffeners in an orthotropic plated bridge deck on concerning the connection between the deck plate and the web of a microscopic scale. An impor...This paper reports the results of experimental research the longitudinal stiffeners in an orthotropic plated bridge deck on concerning the connection between the deck plate and the web of a microscopic scale. An important number of test specimens of a weld are studied with the help of a video microscope, to detect the efficiency of the root of the weld. The second part of the paper is concerned with parametric analysis of the lack of weld penetration by using accurate finite element modelling. The results demonstrate that the weld quality often required can not always be assured, which surely has important consequence on the stresses in the weld and the fatigue resistance.展开更多
The paper describes assessment of the performance of cement-poor concretes on the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimi...The paper describes assessment of the performance of cement-poor concretes on the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimizing the mutual chemical impact on the contacting clay seals. The composition is examined by application of packing theory with respect to the cement/aggregate ratio and the gradation of the aggregate material which is crushed quartzite for providing high internal friction after maturation, as well as to talc added for fluidity and to the small amount of cement. Low porosity and micro-structural stability must be guaranteed for very long periods of time. The study exemplifies how packing theory assist designers in selecting optimal proportions of the various components. Optimum particle packing implies minimizing the porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles. The use of talc as inorganic super-plasticizer since ordinary organic additives for reaching high fluidity at casting are undesirable, and since talc reacts with cement and provides high strength in along-term perspective.展开更多
Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to co...Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to code the composite pack- channels efficiently. For the composite fading environ- ment with muhiple receivers, receivers experience different fading at any time. It＇ s very important to code the composite packet so that intended receivers are in good channel qualities, because in- tended receivers in deep fading have little opportunity to receive the composite packet correctly. Hence, we propose a novel composite packet coding principle of maximizing the total SNR of intend- ed receivers. Since the proposed principle is an NP-complete problem, an efficient heuristic algo- rithm with low complexity is given for finding a suboptimal solution. Simulation results show the heu- ristic based scheme achieves higher transmission efficiency than other network coding-based schemes due to the multi-user diversity gain.展开更多
Objective: To evaluate the safety and effectiveness of eyelid margin cleaning using Deep Cleaning Device for the treatment of meibomian gland dysfunction-associated dry eye. Methods: This was a prospective, randomized...Objective: To evaluate the safety and effectiveness of eyelid margin cleaning using Deep Cleaning Device for the treatment of meibomian gland dysfunction-associated dry eye. Methods: This was a prospective, randomized, open-label, investigator-masked, and self-controlled study. We randomly assigned one eye of patients with meibomian gland dysfunction-associated dry eye to the treatment group, and the other eye to the control group. Both groups received artificial tears and lid warming;the treatment group received an additional one-time in-office eyelid margin cleaning using Deep Cleaning Device. Non-invasive tear break-up time(NITBUT) and tear meniscus height(TMH) of each eye, and Standard Patient Evaluation for Eye Dryness II(SPEED II) score of each patient were evaluated before and at one week after treatment. Results: Thirty eyes of 15 patients were enrolled. No adverse effects occurred during the treatment. Compared with the baseline values, the SPEED score decreased significantly at one week after treatment(mean±95% confidence interval, 11.00±0.99 vs. 5.67±1.67, P<0.0001), the NITBUT-first in the treatment group increased significantly at one week after treatment((4.74±1.27) s vs.(7.49±2.22) s, P=0.01). The NITBUT-first was significantly longer in the treatment group((7.49±2.22) s) than in the control group((5.17±0.91) s) at one week after treatment(P=0.042). No significant differences were found in other tear film parameters between the two groups. Conclusions: Eyelid margin cleaning using the novel Deep Cleaning Device is a convenient, effective, and safe treatment for patients with meibomian gland dysfunction-associated dry eye.展开更多
Floating production storage and offloading （FPSO） units increasingly represent a practical and economic means for deep-water oil extraction and production. Systems thinking gives a unique opporamity to seek a balanc...Floating production storage and offloading （FPSO） units increasingly represent a practical and economic means for deep-water oil extraction and production. Systems thinking gives a unique opporamity to seek a balance between FPSO technical performance（s）, with whole-cost; stakeholder decision-making is charged to align different fit-for-use design specification options＇ that address technical-motion（s）, with respective life-cycle cost analyses （LCCA）. Soft system methodology allows situation based analyses over set periods-of-time by diagnosing the problem-at-hand; namely, assessing the antecedents of life-cycle cost relative to FPSO sub- component design alternatives. Alternative mooring- component comparisons for either new-build hulls or refurbished hulls represent an initial necessary considera- tion to facilitate extraction, production and storage of deep- water oil reserves. Coupled dynamic analysis has been performed to generate FPSO motion in six degrees of freedom using SESAM DeepC, while life-cycle cost analysis （LCAA） studies give net-present-value comparsons reflective of market conditions. A parametric study has been conducted by varying wave heights from 4 - 8 m to understand FPSO motion behavior in the presence of wind and current, as well as comparing the motions of turreted versus spread mooring design alternatives. LCCA data has been generated to compare the cost of such different mooring options/hull conditions over 10 and 25- year periods. Systems thinking has been used to explain the interaction of problem variables; resultantly this paper is able to identify explicit factors affecting the choice of FPSO configurations in terms of motion and whole-cost, toward assisting significantly with the front-end engineering design （FEED） phase of fit-for-purpose configured FPSOs, in waters off Malaysia and Australia.展开更多
基金Project(50675226) supported by the National Natural Science Foundation of China Project(DYXM-115-04-02-01) supported by the Eleventh Five-Year Plan of China
文摘In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave compensation system,the lifting pipe simulator,the buffer simulator and the water pool.The tests ofmining ship motion simulator show that it is able to perform under the predetermined attitude path smoothly and can meet the requirements of themining ship motions.The heave compensation effect is more than 60% under random wave and the goal is set to be 50%.The model test results indicate that this heave compensation system is effective and feasible.
文摘Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.
文摘This paper reports the results of experimental research the longitudinal stiffeners in an orthotropic plated bridge deck on concerning the connection between the deck plate and the web of a microscopic scale. An important number of test specimens of a weld are studied with the help of a video microscope, to detect the efficiency of the root of the weld. The second part of the paper is concerned with parametric analysis of the lack of weld penetration by using accurate finite element modelling. The results demonstrate that the weld quality often required can not always be assured, which surely has important consequence on the stresses in the weld and the fatigue resistance.
文摘The paper describes assessment of the performance of cement-poor concretes on the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimizing the mutual chemical impact on the contacting clay seals. The composition is examined by application of packing theory with respect to the cement/aggregate ratio and the gradation of the aggregate material which is crushed quartzite for providing high internal friction after maturation, as well as to talc added for fluidity and to the small amount of cement. Low porosity and micro-structural stability must be guaranteed for very long periods of time. The study exemplifies how packing theory assist designers in selecting optimal proportions of the various components. Optimum particle packing implies minimizing the porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles. The use of talc as inorganic super-plasticizer since ordinary organic additives for reaching high fluidity at casting are undesirable, and since talc reacts with cement and provides high strength in along-term perspective.
文摘Recent research shows using network sion efficiency in wireless networks greatly et for retransmission over composite fading coding for reliable multicast can improve the retransmis- In this paper, we study how to code the composite pack- channels efficiently. For the composite fading environ- ment with muhiple receivers, receivers experience different fading at any time. It＇ s very important to code the composite packet so that intended receivers are in good channel qualities, because in- tended receivers in deep fading have little opportunity to receive the composite packet correctly. Hence, we propose a novel composite packet coding principle of maximizing the total SNR of intend- ed receivers. Since the proposed principle is an NP-complete problem, an efficient heuristic algo- rithm with low complexity is given for finding a suboptimal solution. Simulation results show the heu- ristic based scheme achieves higher transmission efficiency than other network coding-based schemes due to the multi-user diversity gain.
基金Project supported by the Key Research&Development Projects of Zhejiang Province(No.2018C03082)the Health Commission of Zhejiang Province(Nos.WKJ-ZJ-1905 and 2018ZD007),China
文摘Objective: To evaluate the safety and effectiveness of eyelid margin cleaning using Deep Cleaning Device for the treatment of meibomian gland dysfunction-associated dry eye. Methods: This was a prospective, randomized, open-label, investigator-masked, and self-controlled study. We randomly assigned one eye of patients with meibomian gland dysfunction-associated dry eye to the treatment group, and the other eye to the control group. Both groups received artificial tears and lid warming;the treatment group received an additional one-time in-office eyelid margin cleaning using Deep Cleaning Device. Non-invasive tear break-up time(NITBUT) and tear meniscus height(TMH) of each eye, and Standard Patient Evaluation for Eye Dryness II(SPEED II) score of each patient were evaluated before and at one week after treatment. Results: Thirty eyes of 15 patients were enrolled. No adverse effects occurred during the treatment. Compared with the baseline values, the SPEED score decreased significantly at one week after treatment(mean±95% confidence interval, 11.00±0.99 vs. 5.67±1.67, P<0.0001), the NITBUT-first in the treatment group increased significantly at one week after treatment((4.74±1.27) s vs.(7.49±2.22) s, P=0.01). The NITBUT-first was significantly longer in the treatment group((7.49±2.22) s) than in the control group((5.17±0.91) s) at one week after treatment(P=0.042). No significant differences were found in other tear film parameters between the two groups. Conclusions: Eyelid margin cleaning using the novel Deep Cleaning Device is a convenient, effective, and safe treatment for patients with meibomian gland dysfunction-associated dry eye.
文摘Floating production storage and offloading （FPSO） units increasingly represent a practical and economic means for deep-water oil extraction and production. Systems thinking gives a unique opporamity to seek a balance between FPSO technical performance（s）, with whole-cost; stakeholder decision-making is charged to align different fit-for-use design specification options＇ that address technical-motion（s）, with respective life-cycle cost analyses （LCCA）. Soft system methodology allows situation based analyses over set periods-of-time by diagnosing the problem-at-hand; namely, assessing the antecedents of life-cycle cost relative to FPSO sub- component design alternatives. Alternative mooring- component comparisons for either new-build hulls or refurbished hulls represent an initial necessary considera- tion to facilitate extraction, production and storage of deep- water oil reserves. Coupled dynamic analysis has been performed to generate FPSO motion in six degrees of freedom using SESAM DeepC, while life-cycle cost analysis （LCAA） studies give net-present-value comparsons reflective of market conditions. A parametric study has been conducted by varying wave heights from 4 - 8 m to understand FPSO motion behavior in the presence of wind and current, as well as comparing the motions of turreted versus spread mooring design alternatives. LCCA data has been generated to compare the cost of such different mooring options/hull conditions over 10 and 25- year periods. Systems thinking has been used to explain the interaction of problem variables; resultantly this paper is able to identify explicit factors affecting the choice of FPSO configurations in terms of motion and whole-cost, toward assisting significantly with the front-end engineering design （FEED） phase of fit-for-purpose configured FPSOs, in waters off Malaysia and Australia.
