C 语言是90年代最流行的。通用计算机程序设计语言,仅微机上的 C 语言编译系统就有多种。C 语言的整型变量(包括短整型 short、普通整型 int、长整型 long、甚至字符型 char)都可定义为有符号(signed)和无符号(unsigned)两种。为简单起...C 语言是90年代最流行的。通用计算机程序设计语言,仅微机上的 C 语言编译系统就有多种。C 语言的整型变量(包括短整型 short、普通整型 int、长整型 long、甚至字符型 char)都可定义为有符号(signed)和无符号(unsigned)两种。为简单起见,下面以普通整型为例来说明有符号和无符号两种变量的本质区别。首先,请看一个简单的小程序:main(){signed int m;unsigend int n;m=-1;n=+1;if(m】n) printf("m】n is True!");else printf("m】n is False!");}它的运行结果是"m】n is False!"还是"m】n isFalse!"呢?从程序对变量 m 和 n 的赋值可知:m】n展开更多
Tropical cyclone (TC) center locating is crucial because it lays the foundation for TC forecasting. Locating TC centers, usually by manual means, continues to present many difficulties. Not least is the problem of inc...Tropical cyclone (TC) center locating is crucial because it lays the foundation for TC forecasting. Locating TC centers, usually by manual means, continues to present many difficulties. Not least is the problem of inconsistency between TC center locations forecast by different agencies. In this paper, an objective TC center locating scheme is developed, using infrared satellite images. We introduce a pattern-matching concept, which we illustrate using a spiral curve model. A spiral band model, based on a spiral band region, is designed to extract the spiral cloud-rain bands (SCRBs) of TCs. We propose corresponding criteria on which to score the fitting value of a candidate template defined by our models. In the proposed scheme, TC location is an optimization problem, solved by an ant colony optimization algorithm. In numerical experiments, a minimal mean distance error of 17.9 km is obtained when the scheme is tested against best-track data. The scheme is suitable for TCs with distinct SCRBs or symmetrical central dense overcast, and for TCs both with and without clear eyes.展开更多
The pulse phase and doppler frequency estimation of X-ray pulsars in dynamic situations and its application in navigation is a problem that has not been fully investigated. In this paper, solutions are proposed to sol...The pulse phase and doppler frequency estimation of X-ray pulsars in dynamic situations and its application in navigation is a problem that has not been fully investigated. In this paper, solutions are proposed to solve this problem under conditions of spacecraft and binary motion. A high-precision doppler frequency (velocity) measurement model as well as a phase (range) measurement model is established. The averaged maximum-likelihood estimator is developed for the dynamic pulse phase estimation. The pulse phase tracking technique is used in the doppler frequency determination. The tracking filter is redesigned and compared with the existing algorithms. The comparison verifies the advantage of the filter algorithm presented in this pa- per. Unlike traditional views, it is found that in dynamic situations, shorter observation interval lengths will result in higher-accuracy phase and frequency estimates as the tracking filter outputs. A photon-level integrated numerical simulation is performed. Simulation results testify to the validity of the proposed phase and doppler frequency estimation scheme, and show that incorporation of velocity measurements as well as the range ones into the navigation estimator will improve the navigation steady-state performance.展开更多
A discrete centrosymmetric （H2O）20（CH3OH）4 binary cluster was confined in the cavity of a metaMigand hybrid [Ag4（bpda）2（bpp）4＂ 14H2O.2CH3OH], （1） （where bpp = 1,3-bis（4-pyridyl）propane and H2bpda = 2,2＇...A discrete centrosymmetric （H2O）20（CH3OH）4 binary cluster was confined in the cavity of a metaMigand hybrid [Ag4（bpda）2（bpp）4＂ 14H2O.2CH3OH], （1） （where bpp = 1,3-bis（4-pyridyl）propane and H2bpda = 2,2＇-biphenyldicarboxylic acid） The novel mixed water-methanol cluster consists of one grail-shaped hexadecameric cluster, four dangling water and four hanging methanol molecules. The （H2O）16 cluster is composed of two pairs of edge-sharing （H2O）5 rings attached to one （H2O）4 core with twenty hydrogen bonds. Alternatively, the （H2O）16 cluster is structurally similar to a complicated hydrocarbon generated by undergoing [2＋2] cycloaddition of 1,2,3,4,5,6-hexahydropentalene, which reveals the resemblance between water clusters and organic compounds.展开更多
文摘C 语言是90年代最流行的。通用计算机程序设计语言,仅微机上的 C 语言编译系统就有多种。C 语言的整型变量(包括短整型 short、普通整型 int、长整型 long、甚至字符型 char)都可定义为有符号(signed)和无符号(unsigned)两种。为简单起见,下面以普通整型为例来说明有符号和无符号两种变量的本质区别。首先,请看一个简单的小程序:main(){signed int m;unsigend int n;m=-1;n=+1;if(m】n) printf("m】n is True!");else printf("m】n is False!");}它的运行结果是"m】n is False!"还是"m】n isFalse!"呢?从程序对变量 m 和 n 的赋值可知:m】n
基金supported by National Natural Science Foundation of China (Grant Nos. 60775022 and 60805005)Shanghai Municipal Natural Science Foundation (Grant Nos.09ZR1413700 and No.08ZR1410700)Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 200802481119)
文摘Tropical cyclone (TC) center locating is crucial because it lays the foundation for TC forecasting. Locating TC centers, usually by manual means, continues to present many difficulties. Not least is the problem of inconsistency between TC center locations forecast by different agencies. In this paper, an objective TC center locating scheme is developed, using infrared satellite images. We introduce a pattern-matching concept, which we illustrate using a spiral curve model. A spiral band model, based on a spiral band region, is designed to extract the spiral cloud-rain bands (SCRBs) of TCs. We propose corresponding criteria on which to score the fitting value of a candidate template defined by our models. In the proposed scheme, TC location is an optimization problem, solved by an ant colony optimization algorithm. In numerical experiments, a minimal mean distance error of 17.9 km is obtained when the scheme is tested against best-track data. The scheme is suitable for TCs with distinct SCRBs or symmetrical central dense overcast, and for TCs both with and without clear eyes.
文摘The pulse phase and doppler frequency estimation of X-ray pulsars in dynamic situations and its application in navigation is a problem that has not been fully investigated. In this paper, solutions are proposed to solve this problem under conditions of spacecraft and binary motion. A high-precision doppler frequency (velocity) measurement model as well as a phase (range) measurement model is established. The averaged maximum-likelihood estimator is developed for the dynamic pulse phase estimation. The pulse phase tracking technique is used in the doppler frequency determination. The tracking filter is redesigned and compared with the existing algorithms. The comparison verifies the advantage of the filter algorithm presented in this pa- per. Unlike traditional views, it is found that in dynamic situations, shorter observation interval lengths will result in higher-accuracy phase and frequency estimates as the tracking filter outputs. A photon-level integrated numerical simulation is performed. Simulation results testify to the validity of the proposed phase and doppler frequency estimation scheme, and show that incorporation of velocity measurements as well as the range ones into the navigation estimator will improve the navigation steady-state performance.
基金supported by the National Natural Science Foundation of China(50971063,21053001)the Natural Science Foundation of Fujian Province(2011J01047,2010J01042)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Education of Ministrythe Startup Package Funding of Huaqiao University (10BS210)
文摘A discrete centrosymmetric （H2O）20（CH3OH）4 binary cluster was confined in the cavity of a metaMigand hybrid [Ag4（bpda）2（bpp）4＂ 14H2O.2CH3OH], （1） （where bpp = 1,3-bis（4-pyridyl）propane and H2bpda = 2,2＇-biphenyldicarboxylic acid） The novel mixed water-methanol cluster consists of one grail-shaped hexadecameric cluster, four dangling water and four hanging methanol molecules. The （H2O）16 cluster is composed of two pairs of edge-sharing （H2O）5 rings attached to one （H2O）4 core with twenty hydrogen bonds. Alternatively, the （H2O）16 cluster is structurally similar to a complicated hydrocarbon generated by undergoing [2＋2] cycloaddition of 1,2,3,4,5,6-hexahydropentalene, which reveals the resemblance between water clusters and organic compounds.
