In this paper,we consider the forced neutral advanced dynamic equations with positive and negative coeffcients[x(t)-R(t)x(t+r)]+P(t)x(t+τ)△Q(t)x(t+δ)= f(t),t≥t0 on a time scale T.Several suffcient conditions are o...In this paper,we consider the forced neutral advanced dynamic equations with positive and negative coeffcients[x(t)-R(t)x(t+r)]+P(t)x(t+τ)△Q(t)x(t+δ)= f(t),t≥t0 on a time scale T.Several suffcient conditions are obtained for the oscillation of the dynamic equations.The main result is illustrated by an example.展开更多
Background:There is no consensus regarding the influence of prophylactic no.10 lymph node(LN)dissection in patients with advanced gastric cancer(AGC).We aimed to evaluate whether patients with AGC could benefit from n...Background:There is no consensus regarding the influence of prophylactic no.10 lymph node(LN)dissection in patients with advanced gastric cancer(AGC).We aimed to evaluate whether patients with AGC could benefit from no.10 LN dissection and to explore the clinicopathological indicators of no.10 LN metastasis.Methods:We analyzed the data of 218 patients with AGC who underwent standard D2 lymphadenectomy(SD2;n=108)or modified D2 lymphadenectomy(MD2;n=110)between January 2017 and January 2021.In addition,we examined factors influencing no.10 LN metastasis in the SD2 group.Results:Differentiation,tumor location,and no.4 positive LNs were significantly correlated with no.10 LN metastasis(P<0.05).Borrmann classification,differentiation,depth of invasion,LN metastasis(N),and tumor size were found to correlate with survival in univariate analyses.Age,sex,extent of gastrectomy,tumor location,and extent of lymphadenectomy were not associated with survival(P>0.05).The median survival times were 72.23 and 68.56months for the SD2 andMD2 groups,respectively(P=0.635).Postoperative major morbidity and mortality rates were 37.96%and 3.70%in the SD2 group,and 23.64%and 1.82%in the MD2 group,respectively.Conclusions:Based on our findings,prophylactic no.10 lymphadenectomy may be recommended in patients with AGC who exhibit positive no.4 LN status,poor differentiation,and tumors located on the greater curvature.展开更多
In this paper,efficient signal detectors are designed for Orthogonal Time Frequency Space(OTFS)modulation with Index Modulation(IM)systems.Firstly,the Minimum Mean Squared Error(MMSE)based linear equalizer and its cor...In this paper,efficient signal detectors are designed for Orthogonal Time Frequency Space(OTFS)modulation with Index Modulation(IM)systems.Firstly,the Minimum Mean Squared Error(MMSE)based linear equalizer and its corresponding soft-aided decision are studied for OTFS-IM.To further improve the performance,a Vectorby-Vector-aided Message Passing(VV-MP)detector and its associated soft-decision are proposed,where each IM symbol is considered an entire vector utilized for message calculation and passing.Simulation results are shown that the OTFS-IM system relying on the proposed detectors is capable of providing considerable Bit Error Rate(BER)performance gains over the OTFS and Orthogonal Frequency Division Multiplex(OFDM)with IM systems.展开更多
The topic of "China’s foreign policy under new circumstances" for discussion raised by Experts Forum of Contemporary International Relations is very important, because situation determines tasks, tasks prod...The topic of "China’s foreign policy under new circumstances" for discussion raised by Experts Forum of Contemporary International Relations is very important, because situation determines tasks, tasks produce policies and foreign policy is the continuation of domestic policy.展开更多
An advanced Gauss pseudospectral method(AGPM) was proposed to estimate the parameters of the continuous-time(CT)Hammerstein model.The nonlinear part of the Hammerstein system is approximated with pseudospectral approx...An advanced Gauss pseudospectral method(AGPM) was proposed to estimate the parameters of the continuous-time(CT)Hammerstein model.The nonlinear part of the Hammerstein system is approximated with pseudospectral approximation method.The linear part was written as a controllable canonical form to circumvent the high order time-derivative of the input and output(I/O) signals,which could multiply the measurement noise in the identification procession.Furthermore,an output error minimization was constructed for the CT Hammerstein model identification,which was then transcribed into a nonlinear programming(NLP) problem by AGPM.AGPM could converge to the true values of the CT Hammerstein model with few interpolated Legendre-Gauss(LG) nodes.Lastly,two illustrative examples were proposed to verify the accuracy and efficiency of the method.展开更多
BACKGROUND It is unclear whether treatment delay affects the clinical outcomes of chemotherapy in advanced gastric cancer(A-GC).AIM To assess whether treatment delay affects the clinical outcomes of chemotherapy in A-...BACKGROUND It is unclear whether treatment delay affects the clinical outcomes of chemotherapy in advanced gastric cancer(A-GC).AIM To assess whether treatment delay affects the clinical outcomes of chemotherapy in A-GC.METHODS This single-center retrospective study examined consecutive patients with A-GC between April 2012 and July 2018. In total, 110 patients with stage Ⅳ A-GC who underwent chemotherapy were enrolled. We defined the wait time(WT) as the interval between diagnosis and chemotherapy initiation. We evaluated the influence of WT on overall survival(OS).RESULTS The mean OS was 303 d. The median WT was 17 d. We divided the patients into early and elective WT groups, with a 2-wk cutoff point. There were 46 and 64 patients in the early and elective WT groups, respectively. Compared with the elective WT group, the early WT group had significantly lower albumin(Alb)levels and higher neutrophil/lymphocyte ratios and C-reactive protein(CRP)levels but not a lower performance status. The elective WT group underwent more combination chemotherapy than did the early WT group. OS was different between the two groups(230 d vs 340 d, respectively). Multivariate analysis revealed that higher CRP levels, lower Alb levels and monotherapy were significantly related to a poor prognosis. To minimize potential selection bias,patients in the elective WT group were 1:1 propensity score matched with patients in the early WT group; no significant difference in OS was found(303 d vs 311 d, respectively, log-rank P = 0.9832).CONCLUSION A longer WT in patients with A-GC does not appear to be associated with a worse prognosis.展开更多
A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep ...A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep a higher pressure gradient, which is an effective way to develop low-permeability reservoir. Based on the mechanism of advanced water injection and characteristic of porous flow in low permeability reservoir, a seepage model considering threshold pressure gradient is established to determine the formation pressure distribution at anytime as the water is injected at a constant speed. The optimum water injection time for the advanced water injection technology can be determined by using this model. The calculated result coincides basically with the numerical simulation result, which indicates that the model put forward in this paper is feasible.展开更多
Objective: To investigate the clinical significance of MET gene amplification in patients with gastric cancer in the palliative setting.Methods: MET amplification was assessed using fluorescence in situ hybridization(...Objective: To investigate the clinical significance of MET gene amplification in patients with gastric cancer in the palliative setting.Methods: MET amplification was assessed using fluorescence in situ hybridization(FISH) in 50 patients and quantitative polymerase chain reaction(qPCR) in 326 patients;259 patients treated with first-line fluoropyrimidine and platinum were included for survival analysis.Results: The results of FISH and qPCR indicated that the c-MET/CEP7 ratio was correlated with gene copy number. The optimal cutoff value for the copy number using qPCR to detect MET gene amplification with FISH was 5(κ=0.778, P<0.001). Twenty-one out of 326 patients(6.4%) were identified as MET amplification with a copy number of >5 detected by qPCR. MET-amplified gastric cancer was associated with an Eastern Cooperative Oncology Group(ECOG) performance status(PS) score of ≥2(33.3% vs. 10.5% P=0.007), peritoneal metastasis(76.2% vs. 46.2%, P=0.008), and elevated bilirubin levels(28.6% vs. 7.3%, P=0.006). The median overall survival(OS) and progression-free survival(PFS) were 11.9 and 5.6 months, respectively. MET-amplified gastric cancer was not associated with survival outcomes [hazard ratio(HR)=0.68, 95% confidence interval(95% CI): 0.35-1.32,P=0.254 for PFS;HR=0.68, 95% CI: 0.35-1.32, P=0.251 for OS].Conclusions: qPCR can be used to detect MET gene amplification. MET amplification was not a predictor of poor prognosis in patients with metastatic or unresectable gastric cancer.展开更多
Endoscopic Imaging has progressed tremendously over the last few decades. Novel imaging technologies such as high-resolution and high-magnification white light endoscopy, narrow band imaging, optimal band imaging, aut...Endoscopic Imaging has progressed tremendously over the last few decades. Novel imaging technologies such as high-resolution and high-magnification white light endoscopy, narrow band imaging, optimal band imaging, auto? ourescence imaging and optical coherence tomography not only aid the endoscopist in detecting malignant or pre-malignant lesions but also assist in predicting histology. Recently, the introduction of Endocytoscopy (EC) and Confocal Endomicroscopy has taken us into a new realm of diagnostic endoscopy. With the ability to magnify up to 1000 ×, cellular structures can be visualized in real-time. This advance in technology could potentially lead to a paradigm shift negating the need to obtain biopsies. EC is, however, still in the early stages of development and further research needs to be carried out before it can be accepted as standard practice. This review will focus on the diagnostic utility of the Endocytoscope.展开更多
The topological speed of light which may be used to compute the density of ordinary energy and dark energy of the cosmos is replaced by dimensionless quantity taken from Special Relativity. The said quantity may be in...The topological speed of light which may be used to compute the density of ordinary energy and dark energy of the cosmos is replaced by dimensionless quantity taken from Special Relativity. The said quantity may be interpreted as akin to time dilation ergo a notion topologically equivalent to the speed of the passing of time or the difference of elapsed time between two events in Einstein’s Relativity Theory. This results via Newton’s kinetic energy into the well-known observationally confirmed and accurately measured 4.5 and 95.5 percent of ordinary and dark Cosmic Energy density respectively.展开更多
Patients suffering from advanced dementia who have difficulties in eating and swallowing are often tube fed (TF). They suffer, on most occasions, from additional diseases. The effect of tube feeding in advanced dement...Patients suffering from advanced dementia who have difficulties in eating and swallowing are often tube fed (TF). They suffer, on most occasions, from additional diseases. The effect of tube feeding in advanced dementia patients is controversial and is largely discussed in the medical literature. The purpose of the present study, is to report the effect of tube feeding on the survival time in patients with advanced dementia who suffered from additional diseases. One hundred and forty nine patients with Functional Assessment Stage of Alzheimer Disease (FAST) stage 5>, hospitalized in skilled geriatric nursing department between July 2008 and December 2011 were included in the study. Oral and tub feeding was decided following the evaluation by speech therapists at admission. 99 (66.5%) of the patients were tube fed and 50 (33.5%) received oral feeding at admission. The mean age was 80 ± 11. Sixty four percent of the patients were admitted from general hospitals. Comorbidities were significantly higher in the tube fed group, median survival time was 164 days. The median survival time of the OF group was 78 days (χ2 = 0.94;p = 0.33). Prevalence of tube feeding increased significantly from 53.85% to 90.9% in patients with 3 risk factors such as pressure ulcers, low Hgb and low BMI. The survival time of the tube fed patients was longer compared to patients who were orally fed. Tube feeding in patients with dementia continues to be controversial, and additional researchable data are helpful in the decision to insert a tube.展开更多
Considering the characteristics that the fracture conductivity formed by hydraulic fracturing varies across space and time, a new mathematical model was established for seepage flow in tight gas fractured vertical wel...Considering the characteristics that the fracture conductivity formed by hydraulic fracturing varies across space and time, a new mathematical model was established for seepage flow in tight gas fractured vertical wells which takes into account the effects of dual variable conductivity and stress sensitivity. The Blasingame advanced production decline curves of the model were obtained using the finite element method with hybrid elements. On this basis, the effects of fracture space and time dual variable conductivity and stress sensitivity on Blasingame curve were analyzed. The study shows that the space variable conductivity mainly reduces decline curve value at the early stage; the time variable conductivity can result in drops of the production and the production integral curves, leading to a S-shaped curve; dual variable conductivity is the superposition of the effects given by the two variable conductivities; both time and space variable conductivities cannot delay the time with which the formation fluid flow reaches the quasi-steady state. The stress sensitivity reduces the curve value gradually rather than sharply, delaying the time the flow reaching the quasi-steady state. Ignoring the effects of variable conductivity and stress sensitivity will not affect the estimation on well controlled dynamic reserves. However, it can result in large errors in the interpretation of fractures and reservoir parameters. Conventional advanced production decline analyses of a tight gas fractured well in the Sulige gas field showed that the new model is more effective and reliable than the conventional model, and thus it can be widely applied in advanced production decline analysis of wells with the same characteristics in other gas fields.展开更多
To keep coal workers away from the hazardous area with frequent accidents such as the roof fall and rib spalling in an underground coalmine,we put forward the solution with robotized self-moving anchor-supporting unit...To keep coal workers away from the hazardous area with frequent accidents such as the roof fall and rib spalling in an underground coalmine,we put forward the solution with robotized self-moving anchor-supporting unit.The existing research shows that the surrounding rock of the roadway has self-stability,and the early or late support is not conducive to the safe and reliable support of the roadway,so there is a problem of support opportunity.In order to study the supporting effect and the optimal supporting time of the above solution,we established the mechanical coupling model of surrounding rock and advance support,and investigated the surrounding rock deformation and advance support pressure distribution under different reserved roof subsidence by using the numerical simulation software FLAC3D.The results show that the deformation of surrounding rock increases and finally tends to a stable level with the increase of pre settlement of roadway roof,and when the pre settlement of roof is between 8-15 mm,the vertical pressure of the top beam of advance support reaches the minimum value,about 0.58 MPa.Based on the above research,we put forward the optimum supporting time in roadway excavation,and summarized the evaluation method based on the mechanical coupling model of surrounding rock-advance support.展开更多
In this paper, we discuss the driving-response synchronization problem for two memristive neural networks with retarded and advanced arguments under the condition of additional noise. The control law is related to the...In this paper, we discuss the driving-response synchronization problem for two memristive neural networks with retarded and advanced arguments under the condition of additional noise. The control law is related to the linear time-delay feedback term, and the discontinuous feedback term. Moreover, the random different equation is used to prove the stability of this theory. At the end, the simulation results verify the correctness of the theoretical results.展开更多
基金Supported by the the NNSF of China(60404022 60604004) Supported by the Special Projects in Mathematics Funded by Natural Science Foundation of Hebei Province(07M005)
文摘In this paper,we consider the forced neutral advanced dynamic equations with positive and negative coeffcients[x(t)-R(t)x(t+r)]+P(t)x(t+τ)△Q(t)x(t+δ)= f(t),t≥t0 on a time scale T.Several suffcient conditions are obtained for the oscillation of the dynamic equations.The main result is illustrated by an example.
基金supported by the Department of Gastrointestinal Surgery,Xuzhou Central Hospital,Xuzhou,China
文摘Background:There is no consensus regarding the influence of prophylactic no.10 lymph node(LN)dissection in patients with advanced gastric cancer(AGC).We aimed to evaluate whether patients with AGC could benefit from no.10 LN dissection and to explore the clinicopathological indicators of no.10 LN metastasis.Methods:We analyzed the data of 218 patients with AGC who underwent standard D2 lymphadenectomy(SD2;n=108)or modified D2 lymphadenectomy(MD2;n=110)between January 2017 and January 2021.In addition,we examined factors influencing no.10 LN metastasis in the SD2 group.Results:Differentiation,tumor location,and no.4 positive LNs were significantly correlated with no.10 LN metastasis(P<0.05).Borrmann classification,differentiation,depth of invasion,LN metastasis(N),and tumor size were found to correlate with survival in univariate analyses.Age,sex,extent of gastrectomy,tumor location,and extent of lymphadenectomy were not associated with survival(P>0.05).The median survival times were 72.23 and 68.56months for the SD2 andMD2 groups,respectively(P=0.635).Postoperative major morbidity and mortality rates were 37.96%and 3.70%in the SD2 group,and 23.64%and 1.82%in the MD2 group,respectively.Conclusions:Based on our findings,prophylactic no.10 lymphadenectomy may be recommended in patients with AGC who exhibit positive no.4 LN status,poor differentiation,and tumors located on the greater curvature.
基金supported in part by the National Key Research and Development Program of China under Grant 2020YFB1807100in part by the National Natural Science Foundation of China under Grant 62001179in part by the Fundamental Research Funds for the Central Universities under Grant 2020kfyXJJS111.
文摘In this paper,efficient signal detectors are designed for Orthogonal Time Frequency Space(OTFS)modulation with Index Modulation(IM)systems.Firstly,the Minimum Mean Squared Error(MMSE)based linear equalizer and its corresponding soft-aided decision are studied for OTFS-IM.To further improve the performance,a Vectorby-Vector-aided Message Passing(VV-MP)detector and its associated soft-decision are proposed,where each IM symbol is considered an entire vector utilized for message calculation and passing.Simulation results are shown that the OTFS-IM system relying on the proposed detectors is capable of providing considerable Bit Error Rate(BER)performance gains over the OTFS and Orthogonal Frequency Division Multiplex(OFDM)with IM systems.
文摘The topic of "China’s foreign policy under new circumstances" for discussion raised by Experts Forum of Contemporary International Relations is very important, because situation determines tasks, tasks produce policies and foreign policy is the continuation of domestic policy.
文摘An advanced Gauss pseudospectral method(AGPM) was proposed to estimate the parameters of the continuous-time(CT)Hammerstein model.The nonlinear part of the Hammerstein system is approximated with pseudospectral approximation method.The linear part was written as a controllable canonical form to circumvent the high order time-derivative of the input and output(I/O) signals,which could multiply the measurement noise in the identification procession.Furthermore,an output error minimization was constructed for the CT Hammerstein model identification,which was then transcribed into a nonlinear programming(NLP) problem by AGPM.AGPM could converge to the true values of the CT Hammerstein model with few interpolated Legendre-Gauss(LG) nodes.Lastly,two illustrative examples were proposed to verify the accuracy and efficiency of the method.
文摘BACKGROUND It is unclear whether treatment delay affects the clinical outcomes of chemotherapy in advanced gastric cancer(A-GC).AIM To assess whether treatment delay affects the clinical outcomes of chemotherapy in A-GC.METHODS This single-center retrospective study examined consecutive patients with A-GC between April 2012 and July 2018. In total, 110 patients with stage Ⅳ A-GC who underwent chemotherapy were enrolled. We defined the wait time(WT) as the interval between diagnosis and chemotherapy initiation. We evaluated the influence of WT on overall survival(OS).RESULTS The mean OS was 303 d. The median WT was 17 d. We divided the patients into early and elective WT groups, with a 2-wk cutoff point. There were 46 and 64 patients in the early and elective WT groups, respectively. Compared with the elective WT group, the early WT group had significantly lower albumin(Alb)levels and higher neutrophil/lymphocyte ratios and C-reactive protein(CRP)levels but not a lower performance status. The elective WT group underwent more combination chemotherapy than did the early WT group. OS was different between the two groups(230 d vs 340 d, respectively). Multivariate analysis revealed that higher CRP levels, lower Alb levels and monotherapy were significantly related to a poor prognosis. To minimize potential selection bias,patients in the elective WT group were 1:1 propensity score matched with patients in the early WT group; no significant difference in OS was found(303 d vs 311 d, respectively, log-rank P = 0.9832).CONCLUSION A longer WT in patients with A-GC does not appear to be associated with a worse prognosis.
文摘A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep a higher pressure gradient, which is an effective way to develop low-permeability reservoir. Based on the mechanism of advanced water injection and characteristic of porous flow in low permeability reservoir, a seepage model considering threshold pressure gradient is established to determine the formation pressure distribution at anytime as the water is injected at a constant speed. The optimum water injection time for the advanced water injection technology can be determined by using this model. The calculated result coincides basically with the numerical simulation result, which indicates that the model put forward in this paper is feasible.
基金supported by a grant from the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (No. HI12C1785)
文摘Objective: To investigate the clinical significance of MET gene amplification in patients with gastric cancer in the palliative setting.Methods: MET amplification was assessed using fluorescence in situ hybridization(FISH) in 50 patients and quantitative polymerase chain reaction(qPCR) in 326 patients;259 patients treated with first-line fluoropyrimidine and platinum were included for survival analysis.Results: The results of FISH and qPCR indicated that the c-MET/CEP7 ratio was correlated with gene copy number. The optimal cutoff value for the copy number using qPCR to detect MET gene amplification with FISH was 5(κ=0.778, P<0.001). Twenty-one out of 326 patients(6.4%) were identified as MET amplification with a copy number of >5 detected by qPCR. MET-amplified gastric cancer was associated with an Eastern Cooperative Oncology Group(ECOG) performance status(PS) score of ≥2(33.3% vs. 10.5% P=0.007), peritoneal metastasis(76.2% vs. 46.2%, P=0.008), and elevated bilirubin levels(28.6% vs. 7.3%, P=0.006). The median overall survival(OS) and progression-free survival(PFS) were 11.9 and 5.6 months, respectively. MET-amplified gastric cancer was not associated with survival outcomes [hazard ratio(HR)=0.68, 95% confidence interval(95% CI): 0.35-1.32,P=0.254 for PFS;HR=0.68, 95% CI: 0.35-1.32, P=0.251 for OS].Conclusions: qPCR can be used to detect MET gene amplification. MET amplification was not a predictor of poor prognosis in patients with metastatic or unresectable gastric cancer.
文摘Endoscopic Imaging has progressed tremendously over the last few decades. Novel imaging technologies such as high-resolution and high-magnification white light endoscopy, narrow band imaging, optimal band imaging, auto? ourescence imaging and optical coherence tomography not only aid the endoscopist in detecting malignant or pre-malignant lesions but also assist in predicting histology. Recently, the introduction of Endocytoscopy (EC) and Confocal Endomicroscopy has taken us into a new realm of diagnostic endoscopy. With the ability to magnify up to 1000 ×, cellular structures can be visualized in real-time. This advance in technology could potentially lead to a paradigm shift negating the need to obtain biopsies. EC is, however, still in the early stages of development and further research needs to be carried out before it can be accepted as standard practice. This review will focus on the diagnostic utility of the Endocytoscope.
文摘The topological speed of light which may be used to compute the density of ordinary energy and dark energy of the cosmos is replaced by dimensionless quantity taken from Special Relativity. The said quantity may be interpreted as akin to time dilation ergo a notion topologically equivalent to the speed of the passing of time or the difference of elapsed time between two events in Einstein’s Relativity Theory. This results via Newton’s kinetic energy into the well-known observationally confirmed and accurately measured 4.5 and 95.5 percent of ordinary and dark Cosmic Energy density respectively.
文摘Patients suffering from advanced dementia who have difficulties in eating and swallowing are often tube fed (TF). They suffer, on most occasions, from additional diseases. The effect of tube feeding in advanced dementia patients is controversial and is largely discussed in the medical literature. The purpose of the present study, is to report the effect of tube feeding on the survival time in patients with advanced dementia who suffered from additional diseases. One hundred and forty nine patients with Functional Assessment Stage of Alzheimer Disease (FAST) stage 5>, hospitalized in skilled geriatric nursing department between July 2008 and December 2011 were included in the study. Oral and tub feeding was decided following the evaluation by speech therapists at admission. 99 (66.5%) of the patients were tube fed and 50 (33.5%) received oral feeding at admission. The mean age was 80 ± 11. Sixty four percent of the patients were admitted from general hospitals. Comorbidities were significantly higher in the tube fed group, median survival time was 164 days. The median survival time of the OF group was 78 days (χ2 = 0.94;p = 0.33). Prevalence of tube feeding increased significantly from 53.85% to 90.9% in patients with 3 risk factors such as pressure ulcers, low Hgb and low BMI. The survival time of the tube fed patients was longer compared to patients who were orally fed. Tube feeding in patients with dementia continues to be controversial, and additional researchable data are helpful in the decision to insert a tube.
基金Supported by the China National Science and Technology Major Project(2016ZX05015-005)
文摘Considering the characteristics that the fracture conductivity formed by hydraulic fracturing varies across space and time, a new mathematical model was established for seepage flow in tight gas fractured vertical wells which takes into account the effects of dual variable conductivity and stress sensitivity. The Blasingame advanced production decline curves of the model were obtained using the finite element method with hybrid elements. On this basis, the effects of fracture space and time dual variable conductivity and stress sensitivity on Blasingame curve were analyzed. The study shows that the space variable conductivity mainly reduces decline curve value at the early stage; the time variable conductivity can result in drops of the production and the production integral curves, leading to a S-shaped curve; dual variable conductivity is the superposition of the effects given by the two variable conductivities; both time and space variable conductivities cannot delay the time with which the formation fluid flow reaches the quasi-steady state. The stress sensitivity reduces the curve value gradually rather than sharply, delaying the time the flow reaching the quasi-steady state. Ignoring the effects of variable conductivity and stress sensitivity will not affect the estimation on well controlled dynamic reserves. However, it can result in large errors in the interpretation of fractures and reservoir parameters. Conventional advanced production decline analyses of a tight gas fractured well in the Sulige gas field showed that the new model is more effective and reliable than the conventional model, and thus it can be widely applied in advanced production decline analysis of wells with the same characteristics in other gas fields.
基金National Key Basic Research and Development Program Fund project(Grant No.2014CB046306)the Central University Funding Project for Basic Scientific Research Operations(Grant No.2009QJ16)
文摘To keep coal workers away from the hazardous area with frequent accidents such as the roof fall and rib spalling in an underground coalmine,we put forward the solution with robotized self-moving anchor-supporting unit.The existing research shows that the surrounding rock of the roadway has self-stability,and the early or late support is not conducive to the safe and reliable support of the roadway,so there is a problem of support opportunity.In order to study the supporting effect and the optimal supporting time of the above solution,we established the mechanical coupling model of surrounding rock and advance support,and investigated the surrounding rock deformation and advance support pressure distribution under different reserved roof subsidence by using the numerical simulation software FLAC3D.The results show that the deformation of surrounding rock increases and finally tends to a stable level with the increase of pre settlement of roadway roof,and when the pre settlement of roof is between 8-15 mm,the vertical pressure of the top beam of advance support reaches the minimum value,about 0.58 MPa.Based on the above research,we put forward the optimum supporting time in roadway excavation,and summarized the evaluation method based on the mechanical coupling model of surrounding rock-advance support.
文摘In this paper, we discuss the driving-response synchronization problem for two memristive neural networks with retarded and advanced arguments under the condition of additional noise. The control law is related to the linear time-delay feedback term, and the discontinuous feedback term. Moreover, the random different equation is used to prove the stability of this theory. At the end, the simulation results verify the correctness of the theoretical results.