To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary t...To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.展开更多
AIM:To characterize small bowel(SB)tumors detected by capsule endoscopy(CE),and identify missed tumors.METHODS:The study included 145 consecutive patients in whom 150 CEs were performed.Following CE,the medical record...AIM:To characterize small bowel(SB)tumors detected by capsule endoscopy(CE),and identify missed tumors.METHODS:The study included 145 consecutive patients in whom 150 CEs were performed.Following CE,the medical records of the study population were reviewed.Results of double-or single-balloon enteroscopy performed after CE and the results of surgery in all patients operated on were retrieved.The patients were contacted through telephone interviews or postal mail.In addition,the national cancer registry and the polish clinical gastrointestinal stromal tumor(GIST)Registry were searched to identify missed neoplasms.RESULTS:Indications for CE included overt and occult obscure gastrointestinal bleeding(n=81,53.7%),anemia(n=19,12.7%),malabsorption(n=18,12%),abnormal CB follow through(n=9,6%),abdominal pain(n=7,5%),celiac disease(n=5,3%),neuroendocrine tumor(n=3,2%),Crohn’s disease(n=2,<2%),Peutz-Jeghers syndrome(n=2,<2%),other polyposes(n=2,<2%),and diarrhea(n=2,<2%).The capsule reached the colon in 115(76.6%)examinations.In 150 investigations,CE identified 15SB tumors(10%),14 of which were operated on or treated endoscopically.Malignancies included metastatic melanoma(n=1),adenocarcinoma(n=2),and GIST(n=3).Benign neoplasms included dysplastic Peutz-Jeghers polyps(n=4).Non-neoplastic masses included venous malformation(n=1),inflammatory tumors(n=2),and a mass of unknown histology(n=1).During the follow-up period,three additional SB tumors were found(2 GISTs and one mesenteric tumor of undefined nature).The National Cancer Registry and Polish Clinical GIST Registry revealed no additional SB neoplasms in the post-examination period(follow-up:range 4.2-102.5 mo,median 39 mo).The sensitivity of CE for tumor detection was 83.3%,and the negative predictive value was 97.6%.The specificity and positive predictive value were both 100%.CONCLUSION:Neoplasms may be missed by CE,especially in the proximal SB.In overt obscure gastrointestinal bleeding,complementary endoscopic and/or radiologic diagnostic tests are indicated.展开更多
This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-eva...This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-evasion game since satellites in both sides will try their best to capture or escape. In this game, the distance of these two players is small enough so that the highly nonlinear earth-centered gravitational dynamics can be reduced to the linear Clohessy-Wiltshire（CW） equations. The system is then simplified by introducing the zero effort miss variables. Saddle solution is formulated for the pursuit-evasion game and time-to-go is estimated similarly as that for the exoatmospheric interception. Then a vector guidance is derived to ensure that the interception can be achieved in the optimal time. The proposed guidance law is validated by numerical simulations.展开更多
在公务员招聘过程中,如何科学有效地进行人才的安排、分配,也就是让人才与职位或者部门能有效地进行搭配,这是一个关键的问题.利用人才软匹配系统,以CM CM 2004D为例,在既考虑应聘人员意愿,又考虑用人部门期望要求的情况下,建立择优按...在公务员招聘过程中,如何科学有效地进行人才的安排、分配,也就是让人才与职位或者部门能有效地进行搭配,这是一个关键的问题.利用人才软匹配系统,以CM CM 2004D为例,在既考虑应聘人员意愿,又考虑用人部门期望要求的情况下,建立择优按需录用模型,很好地解决了这个问题.展开更多
In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyze...In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyzed when the target and defender using the differential game guidance law based on the linear model.The core ideas underlying the two guidance laws are the attacker evading to a critical safe boundary from the defender,and then maintaining a critical miss distance.The guidance law more appropriate for the attacker to win the game differs according to the initial parameters.Unlike other guidance laws,when using the derived guidance laws there is no need to know the target and the defender’s control efforts.The results of numerical simulations show that the attacker can evade the defender and hit the target successfully by using the proposed derived guidance laws.展开更多
A novel biased proportional navigation guidance （BPNG） law is proposed for the close approach phase, which aims to make the spacecraft rendezvous with the target in specific relative range and direction. Firstly, in...A novel biased proportional navigation guidance （BPNG） law is proposed for the close approach phase, which aims to make the spacecraft rendezvous with the target in specific relative range and direction. Firstly, in order to describe the special guidance requirements, the concept of zero effort miss vector is proposed and the dangerous area where there exists collision risk for safety consideration is defined. Secondly, the BPNG, which decouples the range control and direc- tion control, is designed in the line-of-sight （LOS） rotation coordinate system. The theoretical anal- ysis proves that BPNG meets guidance requirements quite well. Thirdly, for the consideration of fuel consumption, the optimal biased proportional navigation guidance （OBPNG） law is derived by solving the Schwartz inequality. Finally, simulation results show that BPNG is effective for the close approach with the ability of evading the dangerous area and OBPNG consumes less fuel compared with BPNG.展开更多
Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting...Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting up to almost one fourth of existing adenomas. Among reasons accounting for such failures, is the inability to meticulously visualize the colonic mucosa located either proximal to haustral folds or anatomic curves, including the hepatic and splenic flexures. In order to overcome these limitations, various colonoscope attachments aiming to improve mucosal visualization have been developed. All of them-transparent cap, Endocuff, Endocuff Vision and Endorings-are simply mounted onto the distal tip of the scope. In this review article, we introduce the rationale of their development, present their mode of action and discuss in detail the effect of their implementation in the detection of lesions during colonoscopy.展开更多
AIM: To retrospectively compare previous-day vs splitdose preparation in terms of bowel cleanliness and polyp detection in patients referred for polypectomy. METHODS: Fifty patients underwent two colonoscopies: one di...AIM: To retrospectively compare previous-day vs splitdose preparation in terms of bowel cleanliness and polyp detection in patients referred for polypectomy. METHODS: Fifty patients underwent two colonoscopies: one diagnostic in a private clinic and a second for polypectomy in a University Hospital. The latter procedures were performed within 12 wk of the index ones. Examinations were accomplished by two experienced endoscopists, different in each facility. Twenty-seven patients underwent screening/surveillance colonoscopy, while the rest were symptomatic. Previous day bowel preparation was utilized initially and splitdose for polypectomy. Colon cleansing was evaluated using the Aronchick scale. We measured the number of detected polyps, and the polyp miss rates per-polyp.RESULTS: Excellent/good preparation was reported in 38 cases with previous-day preparation(76%) vs 46 with split-dose(92%), respectively(P = 0.03). One hundred and twenty-six polyps were detected initially and 169 subsequently(P < 0.0001); 88 vs 126 polyps were diminutive(P < 0.0001), 25 vs 29 small(P = 0.048) and 13 vs 14 equal or larger than 10 mm. The miss rates for total, diminutive, small and large polyps were 25.4%, 30.1%, 13.7% and 6.6%, respectively. Multivariate analysis revealed that split-dose preparation was significantly associated(OR, P) with increased number of polyps detected overall(0.869, P < 0.001), in the right(0.418, P = 0.008) and in the left colon(0.452, P = 0.02). CONCLUSION: Split-dose preparation improved colon cleansing, enhanced polyp detection and unmasked significant polyp miss rates.展开更多
A(建议用时:6min).With summer holiday just around the corner,it's time to find some good books to read.Here are some you might like to try.The Big Miss($9).The author had been Tiger Woods’coach for six years,and t...A(建议用时:6min).With summer holiday just around the corner,it's time to find some good books to read.Here are some you might like to try.The Big Miss($9).The author had been Tiger Woods’coach for six years,and the book is a behind-the-scenes look into the famous golfer's private life.One reader wrote on Amazon.com,"I'm a big Tiger fan,and I read this in one sitting.Brilliant!"展开更多
基金co-supported by the National Natural Scienc Foundation of China (No. 61172182)
文摘To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.
基金Supported by The Polish Foundation for Gastroenterology
文摘AIM:To characterize small bowel(SB)tumors detected by capsule endoscopy(CE),and identify missed tumors.METHODS:The study included 145 consecutive patients in whom 150 CEs were performed.Following CE,the medical records of the study population were reviewed.Results of double-or single-balloon enteroscopy performed after CE and the results of surgery in all patients operated on were retrieved.The patients were contacted through telephone interviews or postal mail.In addition,the national cancer registry and the polish clinical gastrointestinal stromal tumor(GIST)Registry were searched to identify missed neoplasms.RESULTS:Indications for CE included overt and occult obscure gastrointestinal bleeding(n=81,53.7%),anemia(n=19,12.7%),malabsorption(n=18,12%),abnormal CB follow through(n=9,6%),abdominal pain(n=7,5%),celiac disease(n=5,3%),neuroendocrine tumor(n=3,2%),Crohn’s disease(n=2,<2%),Peutz-Jeghers syndrome(n=2,<2%),other polyposes(n=2,<2%),and diarrhea(n=2,<2%).The capsule reached the colon in 115(76.6%)examinations.In 150 investigations,CE identified 15SB tumors(10%),14 of which were operated on or treated endoscopically.Malignancies included metastatic melanoma(n=1),adenocarcinoma(n=2),and GIST(n=3).Benign neoplasms included dysplastic Peutz-Jeghers polyps(n=4).Non-neoplastic masses included venous malformation(n=1),inflammatory tumors(n=2),and a mass of unknown histology(n=1).During the follow-up period,three additional SB tumors were found(2 GISTs and one mesenteric tumor of undefined nature).The National Cancer Registry and Polish Clinical GIST Registry revealed no additional SB neoplasms in the post-examination period(follow-up:range 4.2-102.5 mo,median 39 mo).The sensitivity of CE for tumor detection was 83.3%,and the negative predictive value was 97.6%.The specificity and positive predictive value were both 100%.CONCLUSION:Neoplasms may be missed by CE,especially in the proximal SB.In overt obscure gastrointestinal bleeding,complementary endoscopic and/or radiologic diagnostic tests are indicated.
基金co-supported by the National Natural Science Foundation of China (Nos.61603115,91438202 and91638301)China Postdoctoral Science Foundation (No.2015M81455)+1 种基金the Open Fund of National Defense Key Discipline Laboratory of Micro-Spacecraft Technology of China (No.HIT.KLOF.MST.201601)the Heilongjiang Postdoctoral Fund of China (No.LBH-Z15085)
文摘This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-evasion game since satellites in both sides will try their best to capture or escape. In this game, the distance of these two players is small enough so that the highly nonlinear earth-centered gravitational dynamics can be reduced to the linear Clohessy-Wiltshire（CW） equations. The system is then simplified by introducing the zero effort miss variables. Saddle solution is formulated for the pursuit-evasion game and time-to-go is estimated similarly as that for the exoatmospheric interception. Then a vector guidance is derived to ensure that the interception can be achieved in the optimal time. The proposed guidance law is validated by numerical simulations.
基金co-supported by the National Natural Science Foundation of China(No.11672093)the Shanghai Aerospace Science and Technology Innovation Foundation,China(No.SAST2016039)
文摘In this paper,two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyzed when the target and defender using the differential game guidance law based on the linear model.The core ideas underlying the two guidance laws are the attacker evading to a critical safe boundary from the defender,and then maintaining a critical miss distance.The guidance law more appropriate for the attacker to win the game differs according to the initial parameters.Unlike other guidance laws,when using the derived guidance laws there is no need to know the target and the defender’s control efforts.The results of numerical simulations show that the attacker can evade the defender and hit the target successfully by using the proposed derived guidance laws.
基金co-supported by the National Natural Science Foundation of China(No.11372345)the National Basic Research Program of China(No.2013CB733100)
文摘A novel biased proportional navigation guidance （BPNG） law is proposed for the close approach phase, which aims to make the spacecraft rendezvous with the target in specific relative range and direction. Firstly, in order to describe the special guidance requirements, the concept of zero effort miss vector is proposed and the dangerous area where there exists collision risk for safety consideration is defined. Secondly, the BPNG, which decouples the range control and direc- tion control, is designed in the line-of-sight （LOS） rotation coordinate system. The theoretical anal- ysis proves that BPNG meets guidance requirements quite well. Thirdly, for the consideration of fuel consumption, the optimal biased proportional navigation guidance （OBPNG） law is derived by solving the Schwartz inequality. Finally, simulation results show that BPNG is effective for the close approach with the ability of evading the dangerous area and OBPNG consumes less fuel compared with BPNG.
文摘Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting up to almost one fourth of existing adenomas. Among reasons accounting for such failures, is the inability to meticulously visualize the colonic mucosa located either proximal to haustral folds or anatomic curves, including the hepatic and splenic flexures. In order to overcome these limitations, various colonoscope attachments aiming to improve mucosal visualization have been developed. All of them-transparent cap, Endocuff, Endocuff Vision and Endorings-are simply mounted onto the distal tip of the scope. In this review article, we introduce the rationale of their development, present their mode of action and discuss in detail the effect of their implementation in the detection of lesions during colonoscopy.
文摘AIM: To retrospectively compare previous-day vs splitdose preparation in terms of bowel cleanliness and polyp detection in patients referred for polypectomy. METHODS: Fifty patients underwent two colonoscopies: one diagnostic in a private clinic and a second for polypectomy in a University Hospital. The latter procedures were performed within 12 wk of the index ones. Examinations were accomplished by two experienced endoscopists, different in each facility. Twenty-seven patients underwent screening/surveillance colonoscopy, while the rest were symptomatic. Previous day bowel preparation was utilized initially and splitdose for polypectomy. Colon cleansing was evaluated using the Aronchick scale. We measured the number of detected polyps, and the polyp miss rates per-polyp.RESULTS: Excellent/good preparation was reported in 38 cases with previous-day preparation(76%) vs 46 with split-dose(92%), respectively(P = 0.03). One hundred and twenty-six polyps were detected initially and 169 subsequently(P < 0.0001); 88 vs 126 polyps were diminutive(P < 0.0001), 25 vs 29 small(P = 0.048) and 13 vs 14 equal or larger than 10 mm. The miss rates for total, diminutive, small and large polyps were 25.4%, 30.1%, 13.7% and 6.6%, respectively. Multivariate analysis revealed that split-dose preparation was significantly associated(OR, P) with increased number of polyps detected overall(0.869, P < 0.001), in the right(0.418, P = 0.008) and in the left colon(0.452, P = 0.02). CONCLUSION: Split-dose preparation improved colon cleansing, enhanced polyp detection and unmasked significant polyp miss rates.
文摘A(建议用时:6min).With summer holiday just around the corner,it's time to find some good books to read.Here are some you might like to try.The Big Miss($9).The author had been Tiger Woods’coach for six years,and the book is a behind-the-scenes look into the famous golfer's private life.One reader wrote on Amazon.com,"I'm a big Tiger fan,and I read this in one sitting.Brilliant!"
