Effective guidance is one of the most important tasks to the performance of air-to-air missile. The fuzzy logic controller is able to perform effectively even in situations where the information about the plant is ina...Effective guidance is one of the most important tasks to the performance of air-to-air missile. The fuzzy logic controller is able to perform effectively even in situations where the information about the plant is inaccurate and the operating conditions are uncertain. Based on the proportional navigation, the fuzzy logic and the genetic algorithm are combined to develop an evolutionary fuzzy navigation law with self-adapt region for the air-to-air missile guidance. The line of sight (LOS) rate and the closing speed between the missile and the target are inputs of the fuzzy controller. The output of the fuzzy controller is the commanded acceleration. Then a nonlinear function based on the conventional fuzzy logic control is imported to change the region. This nonlinear function can be changed with the input variables. So the dynamic change of the fuzzy variable region is achieved. The guidance law is optimized by the genetic algorithm. Simulation results of air-to-air missile attack using MATLAB show that the method needs less acceleration and shorter flying time, and its realization is simple.[KH*3/4D]展开更多
[Objective] The aim was to study the coupling effect of water and phosphate on economic traits of sugarcane. [Method] Taking sugarcane variety ROC22 as tested material,coupling effects of different levels of water sup...[Objective] The aim was to study the coupling effect of water and phosphate on economic traits of sugarcane. [Method] Taking sugarcane variety ROC22 as tested material,coupling effects of different levels of water supply quantity and different levels of phosphorus fertilizer on the yield and quality of sugarcane were studied. Among them,water supply quantity had 3 levels,that was,the water supply quantity per 10 days from the early tillering stage of sugarcane to the end of elongation was 199.5 m3/hm2 (A1),400.5 m3/hm2 (A2) and 600.0 m3/hm2 (A3),respectively; Phosphorus fertilizer as basic fertilizer had 4 levels:P2O5 0 kg/hm2 (B1),120 kg/hm2 (B2),240 kg/hm2 (B3) and 360 kg/hm2 (B4). [Result] Treatment A3B2 in water-fertilizer coupling was more suitable to improve economic traits of sugarcane. [Conclusion] The research results provide theoretical basis for the efficient utilization of water and phosphorus fertilizer in production of Guangxi sugarcane and the cultivation of high-yield and high-glucose sugarcane.展开更多
To perform a systematic review and meta-analysis on clinical outcomes of photodynamic therapy (PDT) in non-resectable cholangiocarcinoma.METHODSIncluded studies compared outcomes with photodynamic therapy and biliary ...To perform a systematic review and meta-analysis on clinical outcomes of photodynamic therapy (PDT) in non-resectable cholangiocarcinoma.METHODSIncluded studies compared outcomes with photodynamic therapy and biliary stenting (PDT group) vs biliary stenting only (BS group) in palliation of non-resectable cholangiocarcinoma. Articles were searched in MEDLINE, PubMed, and EMBASE. Pooled proportions were calculated using fixed and random effects model. Heterogeneity among studies was assessed using the I<sup>2</sup> statistic.RESULTSTen studies (n = 402) that met inclusion criteria were included in this analysis. The P for χ<sup>2</sup> heterogeneity for all the pooled accuracy estimates was > 0.10. Pooled odds ratio for successful biliary drainage (decrease in bilirubin level > 50% within 7days after stenting) in PDT vs BS group was 4.39 (95%CI: 2.35-8.19). Survival period in PDT and BS groups were 413.04 d (95%CI: 349.54-476.54) and 183.41 (95%CI: 136.81-230.02) respectively. The change in Karnofsky performance scores after intervention in PDT and BS groups were +6.99 (95%CI: 4.15-9.82) and -3.93 (95%CI: -8.63-0.77) respectively. Odds ratio for post-intervention cholangitis in PDT vs BS group was 0.57 (95%CI: 0.35-0.94). In PDT group, 10.51% (95%CI: 6.94-14.72) had photosensitivity reactions that were self-limiting. Subgroup analysis of prospective studies showed similar results, except the incidence of cholangitis was comparable in both groups.CONCLUSIONIn palliation of unresectable cholangiocarcinoma, PDT seems to be significantly superior to BS alone. PDT should be used as an adjunct to biliary stenting in these patients.展开更多
The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity...The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.展开更多
AIM To review evidence on the short-term clinical outcomes of laparoscopic(LRR) vs open rectal resection(ORR) for rectal cancer.METHODS A systematic literature search was performed using Cochrane Central Register, MED...AIM To review evidence on the short-term clinical outcomes of laparoscopic(LRR) vs open rectal resection(ORR) for rectal cancer.METHODS A systematic literature search was performed using Cochrane Central Register, MEDLINE, EMBASE, Scopus, Open Grey and Clinical Trials.gov register for randomized clinical trials(RCTs) comparing LRR vs ORR for rectal cancer and reporting short-term clinical outcomes. Articles published in English from January 1, 1995 to June, 30 2016 that met the selection criteria were retrieved and reviewed. The Preferred Reporting Items for Systematic reviews and Meta-Analysis(PRISMA) statements checklist for reporting a systematic review was followed. Random-effect models were used to estimate mean differences and risk ratios. The robustness and heterogeneity of the results were explored by performing sensitivity analyses. The pooledeffect was considered significant when P < 0.05.RESULTS Overall, 14 RCTs were included. No differences were found in postoperative mortality(P = 0.19) and morbidity(P = 0.75) rates. The mean operative time was 36.67 min longer(95%CI: 27.22-46.11, P < 0.00001), the mean estimated blood loss was 88.80 ml lower(95%CI:-117.25 to-60.34, P < 0.00001), and the mean incision length was 11.17 cm smaller(95%CI:-13.88 to-8.47, P < 0.00001) for LRR than ORR. These results were confirmed by sensitivity analyses that focused on the four major RCTs. The mean length of hospital stay was 1.71 d shorter(95%CI:-2.84 to-0.58, P < 0.003) for LRR than ORR. Similarly, bowel recovery(i.e., day of the first bowel movement) was 0.68 d shorter(95%CI:-1.00 to-0.36, P < 0.00001) for LRR. The sensitivity analysis did not confirm a significant difference between LRR and ORR for these latter two parameters. The overall quality of the evidence was rated as high. CONCLUSION LRR is associated with lesser blood loss, smaller incision length, and longer operative times compared to ORR. No differences are observed for postoperative morbidity and mortality.展开更多
The electronic properties of sphalerite(110) surface with Zn-vacancy and S-vacancy were calculated by using density-functional theory,and the effects of vacancy defect on the copper activation of sphalerite were inves...The electronic properties of sphalerite(110) surface with Zn-vacancy and S-vacancy were calculated by using density-functional theory,and the effects of vacancy defect on the copper activation of sphalerite were investigated.The calculated results indicate that surface state occurs in the band gap of Zn-vacancy sphalerite,which is from the contribution of S 3p orbital at the first layer of the surface.The presence of S-vacancy results in surface state appearing near the Fermi level and the bottom of conductor band,which are composed of S 3p and Zn 4s orbital,respectively.The surface structure of Zn-vacancy sphalerite is more stable than S-vacancy surface due to the occupation of Zn-vacancy by Cu atoms;hence,the substitution reaction of Cu for Zn vacancy is easier than the substitution of Cu for Zn atoms with S-vacancy surface.展开更多
A comprehensive first principles study of III-Antimonide binary compounds is hardly found in literature. We report a broad study of structural and electronic properties of boron antimonide （BSb）, aluminium antimoni...A comprehensive first principles study of III-Antimonide binary compounds is hardly found in literature. We report a broad study of structural and electronic properties of boron antimonide （BSb）, aluminium antimonide （AlSb）, gallium antimonide （GaSb） and indium antimonide （InSb） in zineblende phase based on density functional theory （DFT）. Our calculations are based on Full-PotentiM Lineaxized Augmented Plane wave plus local orbitals （FP- L（APWq-lo）） method. Different forms of exchange-correlation energy functional and corresponding potential are employed for structural and electronic properties. Our computed results for lattice parameters, bulk moduli, their pressure derivatives, and cohesive energy are consistent with the available experimental data. Boron antimonide is found to be the hardest compound of this group. For band structure calculations, in addition to LDA and GGA, we used GGA-EV, an approximation employed by Engel and Vosko. The band gap results with GGA-EV are of significant improvement over the earlier work.展开更多
In the present paper the Lie symmetrical non-Noether conserved quantity of the Poincaré Chetaev equations of a generalized classical mechanics under the general infinitesimal transformations of Lie groups is disc...In the present paper the Lie symmetrical non-Noether conserved quantity of the Poincaré Chetaev equations of a generalized classical mechanics under the general infinitesimal transformations of Lie groups is discussed. First, we establish the determining equations of Lie symmetry of the equations. Second, the Lie symmetrical non-Noether conserved quantity of the equations is deduced. Finally, an example is given to illustrate the application of the results.展开更多
In the framework of the relativistic mean field theory （RMFT）, the relativistic energy losses of the direct Urea processes with hyperons （Y-DURCA ） for reactions A → p ＋ e ＋ υe and ≡^-→ A＋e＋υe are studied...In the framework of the relativistic mean field theory （RMFT）, the relativistic energy losses of the direct Urea processes with hyperons （Y-DURCA ） for reactions A → p ＋ e ＋ υe and ≡^-→ A＋e＋υe are studied in neutron stars. We calculate the energy gap of A hyperons and investigate the effects of the ^1S0 superfluidity （SF） of A hyperons on the Y-DURCA processes. The calculated results are in line with the recent experimental data △ BAA ～ 1.01 ±0.20-0.11^＋0.18 MeV. The results indicate that the ^1S0 SF of A hyperons exists in most density ranges of happening the two reactions. The theoretical cooling curves are in agreement with observation data.展开更多
With a weak hyperon-hyperon （YY） interaction deduced from the new experimental data of AA potential, this paper has performed a calculation of the direct Urca （DURCA） processes in the framework of the relativistic...With a weak hyperon-hyperon （YY） interaction deduced from the new experimental data of AA potential, this paper has performed a calculation of the direct Urca （DURCA） processes in the framework of the relativistic mean field theory （RMFT） including σ＊ and φ mesons, in comparison with the results calculated with the strong YY interaction and with no （σ＊ ,φ ） mesons included. In neutron star matter, the weak YY interaction supplies the additional repulsive interaction between hyperons while the strong YY interaction supplies the attractive one. With the weak YY interaction, the effective masses of hyperons are larger than those with the strong YY interaction while smaller than those with no （σ＊ ,φ） mesons included. The threshold star masses for the DURCA processes involving nucleons and A are not sensitive to the strength of the YY interaction. The weak YY interaction leads to larger threshold masses for the DURCA process involving [1]1 and [1]0 than the other two cases. The process involving [1]0 can take place in the neutron star only when the weak YY interaction is used. The weak YY interaction is able to bring in the agreement with the observation of the neutron star with larger mass and faster cooling than the strong YY interaction.展开更多
The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,...The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,and O-C(=O)-NCS being trans,cis,and cis arranged,respectively)and GCC(gauche,cis,and cis arrangement of the C-C-O-C,C-O-C=O,and O-C(=O)-NCS)have been measured and assigned.The measurements of13C,15N and34S mono-substituted species of the two conformers have also been performed.The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and14N quadrupole coupling constants,which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate.For conformer TCC,the values of Pcckeep constant upon isotopic substitution,indicating that the heavy atoms of TCC are effectively located in the ab plane.展开更多
Public procurement （PP） is considered as one of the key most important functions of any government across the world. Over the years, it has been argued by the scholars that third party engagement （except government...Public procurement （PP） is considered as one of the key most important functions of any government across the world. Over the years, it has been argued by the scholars that third party engagement （except government officials and bidders） in procurement system facilitates to achieve good governance in this sector. In this regard, it is generally expected that third-party monitoring （TPM） of PP, especially monitoring by citizens might earn the trust and confidence of the people in government activities. This study aims at exploring the roles of media in promoting citizen engagement （CE） in PP in order to make the procurement process impartial, efficient, effective, and accountable. The study uses a qualitative methodology in conducting the research with the data being collected through key informant interview, semi-structured interviews, Focus Group Discussions （FGD）, secondary document, and literature reviews. The findings of this study suggest that if the media can play an effective role, the procurement literacy rate will be increasing. Hence, an enabling environment could be created where people will feel at ease to talk about compliance with procurement rules and acts. Hence, media may act as a catalyst to promote citizens involvement in the PP process to hold the respective groups accountable for their activities.展开更多
The electronic structure and optical properties of VO2 and Au-VO2 were studied using density functional theory. The calculation results show that the interaction between Au and O is stronger than that between V and O....The electronic structure and optical properties of VO2 and Au-VO2 were studied using density functional theory. The calculation results show that the interaction between Au and O is stronger than that between V and O. There exists not only the covalent bonding but also ionic bonding in Au--O bond. The band gap of Au-VO2 is smaller than that of VO〉 while the dielectric constant, conductivity, and intensity of optical absorption of Au-VO2 are larger than those of VO2.展开更多
Utilizing the acoustic emission(AE) technique, an experimental investigation into the damage evolution for steel strand under axial tension was described. The damage evolution model for steel stand relating the damage...Utilizing the acoustic emission(AE) technique, an experimental investigation into the damage evolution for steel strand under axial tension was described. The damage evolution model for steel stand relating the damage evolution to acoustic emission parameters was proposed by incorporating the AE rate process theory. The AE monitoring results indicate that damages occur in both elastic and plastic phases of steel strand. In elastic phase, AE signals are mainly sent out from the micro damage due to the surface friction among the wires of steel strand, while in plastic phase, AE signals emitted from the plastic deformation of wires. In addition, the AE cumulative parameters curves closely resemble the loading curve. The AE cumulative parameters curves can well describe the damage evolution process including the damage occurrence and damage development for steel strands. It is concluded that the AE technique is an effective and useful nondestructive technique for evaluating the damage characteristics of steel strand.展开更多
A new hydraulic system of a novel automatic transmission (AT) was designed. The dimension and structure of valves and cylinders were designed by theoretical calculation. The dynamic simulation model of hydraulic syste...A new hydraulic system of a novel automatic transmission (AT) was designed. The dimension and structure of valves and cylinders were designed by theoretical calculation. The dynamic simulation model of hydraulic system of AT was established by ITI-SimulationX. Simulation results and theoretical design results were compared to confirm the simulation model. Based on the confirmed simulation model, the simulation results of pressure and flow of the hydraulic system were analyzed. The dynamic simulation method is very helpful for designing and analyzing the performance of hydraulic system and further optimization design. The theoretical design method and dynamic simulation model are feasible for the real industrial applications. The research results can be used in hydraulic system design and optimization.展开更多
In order to reduce the disturbance on an authorizing user and lower the competition between cognitive users, assure the normal communication of a cognitive radio system, reliability theory is applied to describe if a ...In order to reduce the disturbance on an authorizing user and lower the competition between cognitive users, assure the normal communication of a cognitive radio system, reliability theory is applied to describe if a channel can be used by a cognitive user or not and the probability that the channel is continually used for a period. Three aspects including space, time domain and frequency domain are united for the research on the distribution of frequency spectrum. The simulation result shows that, in the space domain, time domain, frequency domain algorithm, the transmitted data volume and the total throughput of the system are superior to those in greedy algorithm and time domain—frequency domain algorithm, the novel algorithm is helpful to reduce the disturbance caused by a cognitive user to an authorizing user and lower the competition between cognitive users, this simulation result shows that the proposed algorithm is effective.展开更多
In making purchasing decisions, consumers look to online reviews posted by others who have used or experienced the product/service. Most existing studies on online reviews only focused on their content without address...In making purchasing decisions, consumers look to online reviews posted by others who have used or experienced the product/service. Most existing studies on online reviews only focused on their content without addressing how their explanation type influences purchasing decisions, not to mention the boundary conditions for such effects. Based on three experimental studies, this paper examines how explanation type affects the perceived usefulness of online reviews and purchasing decisions, and discusses the boundary conditions for such effects. Our findings show that positive explanation type has a positive effect on the perceived usefulness of online reviews, while negative explanation has an insignificant impact. For search products, there is a positive correlation between the online reviews of explained actions and the perceived usefulness of consumer reviews. For experience products, there is a positive correlation between the online reviews of explained reactions and the perceived usefulness of consumer reviews. Further research found that temporal distance may moderate the effects of explanation type and product type on the perceived usefulness of online reviews. This study also provides a new approach for research on the word-of-mouth(WOM) with meaningful implications for e-commerce firms.展开更多
Women in Kenya are underrepresented in decision-making positions, which appears as a remnant of persisting cultural gender roles that limit women from participating in activities critical for personal, societal, and n...Women in Kenya are underrepresented in decision-making positions, which appears as a remnant of persisting cultural gender roles that limit women from participating in activities critical for personal, societal, and national development. Such retrogressive ideas regarding a large number of the country＇s citizens have to be addressed early in the life of a girl to build in girls＇ self-esteem and facilitate them to develop leadership skills. This study investigated the extent to which girls in primary schools in Voi sub-county are involved in leadership in their schools. The study was based on the 2010 Kenya＇s constitution which ruled that no more than two-thirds of elected or appointed public institutions leaders should consist of one gender. The new legal framework seeks to break down the barriers women face in realizing their political, civil, economic, and social rights. It also ensures that women are involved in decision-making at all levels of government. In this study, data was collected from three mixed primary schools in Voi sub-county given codes A, B, and C. School A had a total of 470 pupils; 225 were boys and 245 were girls and the school had 21 leadership positions. The findings showed that the majority 14 （66.7%） of the leadership positions were occupied by boys while the few 7 （33.3%） were occupied by girls. In school B, there were a total of 1,056 pupils; 498 were boys and 558 were girls. There were 13 leadership positions. The majority of the positions 7 （53.8 %） were occupied by boys and minority 6 （46.2%） were occupied by girls. In school C, there were a total of 1,450 pupils and 680 were boys and 770 girls. There were 13 leadership positions. The majority 7 （53.8%） of the positions were occupied by boys while 6 （46.2%） were occupied by girls. In all the schools, there were more girls than boys but boys occupied more leadership positions than girls. Boys also took senior positions and girls were their deputies and were not as active as boys in areas such as class discussions and debate. It was recommended that conscious effort should be made to develop leadership skills in girls during their formative years.展开更多
Based on theory of variable-mass system thermodynamics, the dynamic mathematic models of each component of the horizontal steam-launch system were established, and by the numerical simulation of the system launching p...Based on theory of variable-mass system thermodynamics, the dynamic mathematic models of each component of the horizontal steam-launch system were established, and by the numerical simulation of the system launching process, the thermodynamics and kinetics characteristics of the system with three valves of different flow characteristics were got. The simulation results show that the values of the peak-to-average ratios of dimensionless acceleration with the equal percentage valve, the linear valve and the quick opening valve are 1.355, 1.614 and 1.722, respectively, and the final values of the dimensionless velocities are 0.843, 0.957 and 1.0, respectively. In conclusion, the value of the dimensionless velocity with the equal percentage valve doesn't reach the set value of 0.90 when the dimensionless displacement is 0.82, while the system with the linear valve can meet the launching requirement, as well as the fluctuation range of dimensionless acceleration is less than that of the quick opening valve. Therefore, the system with the linear valve has the best performance among the three kinds of valves.展开更多
This study applies the situational theory of publics （STP） to a health crisis by exploring the effect of anger on public behavior. The results of a survey administered on the case of the candlelight rallies on the U...This study applies the situational theory of publics （STP） to a health crisis by exploring the effect of anger on public behavior. The results of a survey administered on the case of the candlelight rallies on the U.S. beef imports in South Korea in 2008 demonstrated that involvement, problem recognition, and constraint recognition predicted communication behaviors as well as various issue-related online and offline behaviors. In addition, anger was found to be a significant driving force for publics to perform the behaviors. The segmented publics showed significantly different levels of anger, information processing and seeking, online behaviors, and participation in the candlelight rallies展开更多
文摘Effective guidance is one of the most important tasks to the performance of air-to-air missile. The fuzzy logic controller is able to perform effectively even in situations where the information about the plant is inaccurate and the operating conditions are uncertain. Based on the proportional navigation, the fuzzy logic and the genetic algorithm are combined to develop an evolutionary fuzzy navigation law with self-adapt region for the air-to-air missile guidance. The line of sight (LOS) rate and the closing speed between the missile and the target are inputs of the fuzzy controller. The output of the fuzzy controller is the commanded acceleration. Then a nonlinear function based on the conventional fuzzy logic control is imported to change the region. This nonlinear function can be changed with the input variables. So the dynamic change of the fuzzy variable region is achieved. The guidance law is optimized by the genetic algorithm. Simulation results of air-to-air missile attack using MATLAB show that the method needs less acceleration and shorter flying time, and its realization is simple.[KH*3/4D]
基金Supported by National Science and Technology Project of China(2007BAD30B04)~~
文摘[Objective] The aim was to study the coupling effect of water and phosphate on economic traits of sugarcane. [Method] Taking sugarcane variety ROC22 as tested material,coupling effects of different levels of water supply quantity and different levels of phosphorus fertilizer on the yield and quality of sugarcane were studied. Among them,water supply quantity had 3 levels,that was,the water supply quantity per 10 days from the early tillering stage of sugarcane to the end of elongation was 199.5 m3/hm2 (A1),400.5 m3/hm2 (A2) and 600.0 m3/hm2 (A3),respectively; Phosphorus fertilizer as basic fertilizer had 4 levels:P2O5 0 kg/hm2 (B1),120 kg/hm2 (B2),240 kg/hm2 (B3) and 360 kg/hm2 (B4). [Result] Treatment A3B2 in water-fertilizer coupling was more suitable to improve economic traits of sugarcane. [Conclusion] The research results provide theoretical basis for the efficient utilization of water and phosphorus fertilizer in production of Guangxi sugarcane and the cultivation of high-yield and high-glucose sugarcane.
文摘To perform a systematic review and meta-analysis on clinical outcomes of photodynamic therapy (PDT) in non-resectable cholangiocarcinoma.METHODSIncluded studies compared outcomes with photodynamic therapy and biliary stenting (PDT group) vs biliary stenting only (BS group) in palliation of non-resectable cholangiocarcinoma. Articles were searched in MEDLINE, PubMed, and EMBASE. Pooled proportions were calculated using fixed and random effects model. Heterogeneity among studies was assessed using the I<sup>2</sup> statistic.RESULTSTen studies (n = 402) that met inclusion criteria were included in this analysis. The P for χ<sup>2</sup> heterogeneity for all the pooled accuracy estimates was > 0.10. Pooled odds ratio for successful biliary drainage (decrease in bilirubin level > 50% within 7days after stenting) in PDT vs BS group was 4.39 (95%CI: 2.35-8.19). Survival period in PDT and BS groups were 413.04 d (95%CI: 349.54-476.54) and 183.41 (95%CI: 136.81-230.02) respectively. The change in Karnofsky performance scores after intervention in PDT and BS groups were +6.99 (95%CI: 4.15-9.82) and -3.93 (95%CI: -8.63-0.77) respectively. Odds ratio for post-intervention cholangitis in PDT vs BS group was 0.57 (95%CI: 0.35-0.94). In PDT group, 10.51% (95%CI: 6.94-14.72) had photosensitivity reactions that were self-limiting. Subgroup analysis of prospective studies showed similar results, except the incidence of cholangitis was comparable in both groups.CONCLUSIONIn palliation of unresectable cholangiocarcinoma, PDT seems to be significantly superior to BS alone. PDT should be used as an adjunct to biliary stenting in these patients.
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (PRC)Foundation of Qufu Normal University under Grant No. XJ0622
文摘The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.
文摘AIM To review evidence on the short-term clinical outcomes of laparoscopic(LRR) vs open rectal resection(ORR) for rectal cancer.METHODS A systematic literature search was performed using Cochrane Central Register, MEDLINE, EMBASE, Scopus, Open Grey and Clinical Trials.gov register for randomized clinical trials(RCTs) comparing LRR vs ORR for rectal cancer and reporting short-term clinical outcomes. Articles published in English from January 1, 1995 to June, 30 2016 that met the selection criteria were retrieved and reviewed. The Preferred Reporting Items for Systematic reviews and Meta-Analysis(PRISMA) statements checklist for reporting a systematic review was followed. Random-effect models were used to estimate mean differences and risk ratios. The robustness and heterogeneity of the results were explored by performing sensitivity analyses. The pooledeffect was considered significant when P < 0.05.RESULTS Overall, 14 RCTs were included. No differences were found in postoperative mortality(P = 0.19) and morbidity(P = 0.75) rates. The mean operative time was 36.67 min longer(95%CI: 27.22-46.11, P < 0.00001), the mean estimated blood loss was 88.80 ml lower(95%CI:-117.25 to-60.34, P < 0.00001), and the mean incision length was 11.17 cm smaller(95%CI:-13.88 to-8.47, P < 0.00001) for LRR than ORR. These results were confirmed by sensitivity analyses that focused on the four major RCTs. The mean length of hospital stay was 1.71 d shorter(95%CI:-2.84 to-0.58, P < 0.003) for LRR than ORR. Similarly, bowel recovery(i.e., day of the first bowel movement) was 0.68 d shorter(95%CI:-1.00 to-0.36, P < 0.00001) for LRR. The sensitivity analysis did not confirm a significant difference between LRR and ORR for these latter two parameters. The overall quality of the evidence was rated as high. CONCLUSION LRR is associated with lesser blood loss, smaller incision length, and longer operative times compared to ORR. No differences are observed for postoperative morbidity and mortality.
基金Project(50864001) supported by the National Natural Science Foundation of China
文摘The electronic properties of sphalerite(110) surface with Zn-vacancy and S-vacancy were calculated by using density-functional theory,and the effects of vacancy defect on the copper activation of sphalerite were investigated.The calculated results indicate that surface state occurs in the band gap of Zn-vacancy sphalerite,which is from the contribution of S 3p orbital at the first layer of the surface.The presence of S-vacancy results in surface state appearing near the Fermi level and the bottom of conductor band,which are composed of S 3p and Zn 4s orbital,respectively.The surface structure of Zn-vacancy sphalerite is more stable than S-vacancy surface due to the occupation of Zn-vacancy by Cu atoms;hence,the substitution reaction of Cu for Zn vacancy is easier than the substitution of Cu for Zn atoms with S-vacancy surface.
文摘A comprehensive first principles study of III-Antimonide binary compounds is hardly found in literature. We report a broad study of structural and electronic properties of boron antimonide （BSb）, aluminium antimonide （AlSb）, gallium antimonide （GaSb） and indium antimonide （InSb） in zineblende phase based on density functional theory （DFT）. Our calculations are based on Full-PotentiM Lineaxized Augmented Plane wave plus local orbitals （FP- L（APWq-lo）） method. Different forms of exchange-correlation energy functional and corresponding potential are employed for structural and electronic properties. Our computed results for lattice parameters, bulk moduli, their pressure derivatives, and cohesive energy are consistent with the available experimental data. Boron antimonide is found to be the hardest compound of this group. For band structure calculations, in addition to LDA and GGA, we used GGA-EV, an approximation employed by Engel and Vosko. The band gap results with GGA-EV are of significant improvement over the earlier work.
文摘In the present paper the Lie symmetrical non-Noether conserved quantity of the Poincaré Chetaev equations of a generalized classical mechanics under the general infinitesimal transformations of Lie groups is discussed. First, we establish the determining equations of Lie symmetry of the equations. Second, the Lie symmetrical non-Noether conserved quantity of the equations is deduced. Finally, an example is given to illustrate the application of the results.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10675024, 11075063the National Fundamental Fund project Subsidy Funds of Personnel Training J0730311
文摘In the framework of the relativistic mean field theory （RMFT）, the relativistic energy losses of the direct Urea processes with hyperons （Y-DURCA ） for reactions A → p ＋ e ＋ υe and ≡^-→ A＋e＋υe are studied in neutron stars. We calculate the energy gap of A hyperons and investigate the effects of the ^1S0 superfluidity （SF） of A hyperons on the Y-DURCA processes. The calculated results are in line with the recent experimental data △ BAA ～ 1.01 ±0.20-0.11^＋0.18 MeV. The results indicate that the ^1S0 SF of A hyperons exists in most density ranges of happening the two reactions. The theoretical cooling curves are in agreement with observation data.
基金Supported by the Natural Science Fundamental Research Project of Jiangsu Colleges and Universities under Grant No.10KJB140002
文摘With a weak hyperon-hyperon （YY） interaction deduced from the new experimental data of AA potential, this paper has performed a calculation of the direct Urca （DURCA） processes in the framework of the relativistic mean field theory （RMFT） including σ＊ and φ mesons, in comparison with the results calculated with the strong YY interaction and with no （σ＊ ,φ ） mesons included. In neutron star matter, the weak YY interaction supplies the additional repulsive interaction between hyperons while the strong YY interaction supplies the attractive one. With the weak YY interaction, the effective masses of hyperons are larger than those with the strong YY interaction while smaller than those with no （σ＊ ,φ） mesons included. The threshold star masses for the DURCA processes involving nucleons and A are not sensitive to the strength of the YY interaction. The weak YY interaction leads to larger threshold masses for the DURCA process involving [1]1 and [1]0 than the other two cases. The process involving [1]0 can take place in the neutron star only when the weak YY interaction is used. The weak YY interaction is able to bring in the agreement with the observation of the neutron star with larger mass and faster cooling than the strong YY interaction.
基金The support from the National Natural Science Foundation of China(No.22273009)Chongqing University。
文摘The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,and O-C(=O)-NCS being trans,cis,and cis arranged,respectively)and GCC(gauche,cis,and cis arrangement of the C-C-O-C,C-O-C=O,and O-C(=O)-NCS)have been measured and assigned.The measurements of13C,15N and34S mono-substituted species of the two conformers have also been performed.The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and14N quadrupole coupling constants,which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate.For conformer TCC,the values of Pcckeep constant upon isotopic substitution,indicating that the heavy atoms of TCC are effectively located in the ab plane.
文摘Public procurement （PP） is considered as one of the key most important functions of any government across the world. Over the years, it has been argued by the scholars that third party engagement （except government officials and bidders） in procurement system facilitates to achieve good governance in this sector. In this regard, it is generally expected that third-party monitoring （TPM） of PP, especially monitoring by citizens might earn the trust and confidence of the people in government activities. This study aims at exploring the roles of media in promoting citizen engagement （CE） in PP in order to make the procurement process impartial, efficient, effective, and accountable. The study uses a qualitative methodology in conducting the research with the data being collected through key informant interview, semi-structured interviews, Focus Group Discussions （FGD）, secondary document, and literature reviews. The findings of this study suggest that if the media can play an effective role, the procurement literacy rate will be increasing. Hence, an enabling environment could be created where people will feel at ease to talk about compliance with procurement rules and acts. Hence, media may act as a catalyst to promote citizens involvement in the PP process to hold the respective groups accountable for their activities.
基金Project(2014GXNSFAA118342)supported by Guangxi Natural Science Foundation,ChinaProject supported by Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,ChinaProject supported by High-level Innovation Team and Outstanding Scholar Program in Guangxi Colleges(the second batch),China
文摘The electronic structure and optical properties of VO2 and Au-VO2 were studied using density functional theory. The calculation results show that the interaction between Au and O is stronger than that between V and O. There exists not only the covalent bonding but also ionic bonding in Au--O bond. The band gap of Au-VO2 is smaller than that of VO〉 while the dielectric constant, conductivity, and intensity of optical absorption of Au-VO2 are larger than those of VO2.
基金Projects(51308073,51378081)supported by the National Natural Science Foundation of ChinaProject(20124316120002)supported by PhD Programs Foundation of Ministry of Education of China+1 种基金Project(12KB02)supported by the Key Laboratory for Safety Control of Bridge Engineering of Ministry of Education of ChinaProject(14JJ3087)supported by the Science Foundation of Hunan Province,China
文摘Utilizing the acoustic emission(AE) technique, an experimental investigation into the damage evolution for steel strand under axial tension was described. The damage evolution model for steel stand relating the damage evolution to acoustic emission parameters was proposed by incorporating the AE rate process theory. The AE monitoring results indicate that damages occur in both elastic and plastic phases of steel strand. In elastic phase, AE signals are mainly sent out from the micro damage due to the surface friction among the wires of steel strand, while in plastic phase, AE signals emitted from the plastic deformation of wires. In addition, the AE cumulative parameters curves closely resemble the loading curve. The AE cumulative parameters curves can well describe the damage evolution process including the damage occurrence and damage development for steel strands. It is concluded that the AE technique is an effective and useful nondestructive technique for evaluating the damage characteristics of steel strand.
基金Project(911901204) supported by Youth Innovation Foundation of Beijing University of Aeronautics and Astronautics
文摘A new hydraulic system of a novel automatic transmission (AT) was designed. The dimension and structure of valves and cylinders were designed by theoretical calculation. The dynamic simulation model of hydraulic system of AT was established by ITI-SimulationX. Simulation results and theoretical design results were compared to confirm the simulation model. Based on the confirmed simulation model, the simulation results of pressure and flow of the hydraulic system were analyzed. The dynamic simulation method is very helpful for designing and analyzing the performance of hydraulic system and further optimization design. The theoretical design method and dynamic simulation model are feasible for the real industrial applications. The research results can be used in hydraulic system design and optimization.
基金supported by Natural Science Foundation of Heilongjiang Province of China(No.F2015017)
文摘In order to reduce the disturbance on an authorizing user and lower the competition between cognitive users, assure the normal communication of a cognitive radio system, reliability theory is applied to describe if a channel can be used by a cognitive user or not and the probability that the channel is continually used for a period. Three aspects including space, time domain and frequency domain are united for the research on the distribution of frequency spectrum. The simulation result shows that, in the space domain, time domain, frequency domain algorithm, the transmitted data volume and the total throughput of the system are superior to those in greedy algorithm and time domain—frequency domain algorithm, the novel algorithm is helpful to reduce the disturbance caused by a cognitive user to an authorizing user and lower the competition between cognitive users, this simulation result shows that the proposed algorithm is effective.
基金Supported by"Reputation Sharing Mechanism and Recourse Liability Policy of E-commerce Platform:An Interactive Perspective of Platform Enterprise and Its Sellers"Project of the National Natural Science Foundation of China(NSFC)(Grant No.71672026)"Influencing Mechanism of User-generated Content on Brand Equity of Multichannel Retailers under the Regulatory Focus Paradigm"of the NSFC(Grant No.71272050)
文摘In making purchasing decisions, consumers look to online reviews posted by others who have used or experienced the product/service. Most existing studies on online reviews only focused on their content without addressing how their explanation type influences purchasing decisions, not to mention the boundary conditions for such effects. Based on three experimental studies, this paper examines how explanation type affects the perceived usefulness of online reviews and purchasing decisions, and discusses the boundary conditions for such effects. Our findings show that positive explanation type has a positive effect on the perceived usefulness of online reviews, while negative explanation has an insignificant impact. For search products, there is a positive correlation between the online reviews of explained actions and the perceived usefulness of consumer reviews. For experience products, there is a positive correlation between the online reviews of explained reactions and the perceived usefulness of consumer reviews. Further research found that temporal distance may moderate the effects of explanation type and product type on the perceived usefulness of online reviews. This study also provides a new approach for research on the word-of-mouth(WOM) with meaningful implications for e-commerce firms.
文摘Women in Kenya are underrepresented in decision-making positions, which appears as a remnant of persisting cultural gender roles that limit women from participating in activities critical for personal, societal, and national development. Such retrogressive ideas regarding a large number of the country＇s citizens have to be addressed early in the life of a girl to build in girls＇ self-esteem and facilitate them to develop leadership skills. This study investigated the extent to which girls in primary schools in Voi sub-county are involved in leadership in their schools. The study was based on the 2010 Kenya＇s constitution which ruled that no more than two-thirds of elected or appointed public institutions leaders should consist of one gender. The new legal framework seeks to break down the barriers women face in realizing their political, civil, economic, and social rights. It also ensures that women are involved in decision-making at all levels of government. In this study, data was collected from three mixed primary schools in Voi sub-county given codes A, B, and C. School A had a total of 470 pupils; 225 were boys and 245 were girls and the school had 21 leadership positions. The findings showed that the majority 14 （66.7%） of the leadership positions were occupied by boys while the few 7 （33.3%） were occupied by girls. In school B, there were a total of 1,056 pupils; 498 were boys and 558 were girls. There were 13 leadership positions. The majority of the positions 7 （53.8 %） were occupied by boys and minority 6 （46.2%） were occupied by girls. In school C, there were a total of 1,450 pupils and 680 were boys and 770 girls. There were 13 leadership positions. The majority 7 （53.8%） of the positions were occupied by boys while 6 （46.2%） were occupied by girls. In all the schools, there were more girls than boys but boys occupied more leadership positions than girls. Boys also took senior positions and girls were their deputies and were not as active as boys in areas such as class discussions and debate. It was recommended that conscious effort should be made to develop leadership skills in girls during their formative years.
基金Project(20080431380)supported by the National Postdoctoral Science Foundation,China
文摘Based on theory of variable-mass system thermodynamics, the dynamic mathematic models of each component of the horizontal steam-launch system were established, and by the numerical simulation of the system launching process, the thermodynamics and kinetics characteristics of the system with three valves of different flow characteristics were got. The simulation results show that the values of the peak-to-average ratios of dimensionless acceleration with the equal percentage valve, the linear valve and the quick opening valve are 1.355, 1.614 and 1.722, respectively, and the final values of the dimensionless velocities are 0.843, 0.957 and 1.0, respectively. In conclusion, the value of the dimensionless velocity with the equal percentage valve doesn't reach the set value of 0.90 when the dimensionless displacement is 0.82, while the system with the linear valve can meet the launching requirement, as well as the fluctuation range of dimensionless acceleration is less than that of the quick opening valve. Therefore, the system with the linear valve has the best performance among the three kinds of valves.
文摘This study applies the situational theory of publics （STP） to a health crisis by exploring the effect of anger on public behavior. The results of a survey administered on the case of the candlelight rallies on the U.S. beef imports in South Korea in 2008 demonstrated that involvement, problem recognition, and constraint recognition predicted communication behaviors as well as various issue-related online and offline behaviors. In addition, anger was found to be a significant driving force for publics to perform the behaviors. The segmented publics showed significantly different levels of anger, information processing and seeking, online behaviors, and participation in the candlelight rallies
