A planar circuit structure, which is based on three cascaded pairs of coupled lines, an open stub, and an isolation resistor, is proposed in this paper to design a compact dual.band balun with high isolation. This cir...A planar circuit structure, which is based on three cascaded pairs of coupled lines, an open stub, and an isolation resistor, is proposed in this paper to design a compact dual.band balun with high isolation. This circuit features equal power division with out of phase, all ports matching, high isolation between two outputs, compact structure, and inherent impedance transformation. The closedform design equations are derived based on the traditional transmission.line theory and even.(odd.) mode analysis. A practical dual.band balun, which operates at 0.9/1.8GHz, is designed and fabricated to validate the function of equal power division with out of phase and high isolation between two outputs. The consistency between the simulated and measured results verify the design theory.展开更多
To solve the safe horizontal transportation by rail&road of remote sensing satellite problem in the process of unpredictable dynamic load,a high attenuation vibration isolation damper(hereinafter referred to as vi...To solve the safe horizontal transportation by rail&road of remote sensing satellite problem in the process of unpredictable dynamic load,a high attenuation vibration isolation damper(hereinafter referred to as vibration isolation damper)was developed.By simulation analysis and transportation test using satellite structural model and engineering prototype,validity and reliability of the vibration isolation damper was verified,which can meet the requirements of vibration and shock from various transportation conditions.展开更多
The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestit...The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestite in mild condition was described.Sr element remained in precipitation with formation of Sr(OH)2,while S element entered into leachate with formation of Na2SO4.The effects of initial concentration of NaOH,conversion temperature,liquid-to-solid(L/S)ratio and conversion time on Sr/S ratio of samples for celestite conversion were systematically investigated by experiments.The results demonstrated that the efficiency of Sr/S isolation increased with the initial concentration of NaOH,L/S ratio and conversion time,and decreased with conversion temperature.The maximum conversion ratio of Sr(OH)2 was 93.88%under the optimum condition,whose Sr/S ratio of sample could reach to 41.16.It illustrated that better isolation efficiency of celestite could be achieved in alkaline treatment.The results of SEM-EDS analyses demonstrated that the conversion reaction was a dissolution-precipitation process.展开更多
High affinity phosphate transporterplays an important role in plantadapting to low phosphorus. Isolationof genes coding this kind of proteinhas attracted worldwide scholars toaccomplish. We aimed to isolate thegene an...High affinity phosphate transporterplays an important role in plantadapting to low phosphorus. Isolationof genes coding this kind of proteinhas attracted worldwide scholars toaccomplish. We aimed to isolate thegene and transfer it to target plants展开更多
In this paper, a co-polarized, co-located electric and magnetic dipoles(CCEMD) with high isolation is presented. The antenna consists of a loop based on segmented line and two independent feeding ports. Two modes of t...In this paper, a co-polarized, co-located electric and magnetic dipoles(CCEMD) with high isolation is presented. The antenna consists of a loop based on segmented line and two independent feeding ports. Two modes of the antenna are exited separately, the first one has a radiation pattern equivalent to an electric dipole by exciting anti-phase current with symmetric distribution, and the second one is like a magnetic dipole by exciting uniform and in-phase currents along the loop. The antenna is fabricated and tested. Its measured common-10 d B impedance bandwidth at two ports is 280 MHz(2.32-2.6 GHz) with isolation better than 41 d B. Its MIMO performance in terms of capacity gain(CG) over the SISO system is investigated in a multipath rich environment containing two parallel PEC planes by both measurements and image theory based simulations. Results show that, in free space, the CG results are just slightly larger than 1, however, in the multipath rich channel, the CG values are very close to 2, which indicates that two separate subchannels can be achieved by the proposed CCEMD. The measured results of CG agree well with that obtained by simulation.展开更多
The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial thr...The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.展开更多
In this paper,a new approach to design terahertz(THz)E-plane crossover coupler is reported.By cascading two symmetrical septum polarizers,a simple structure with wide operating bandwidth and high isolation performance...In this paper,a new approach to design terahertz(THz)E-plane crossover coupler is reported.By cascading two symmetrical septum polarizers,a simple structure with wide operating bandwidth and high isolation performance is achieved.The working principle is explained by operating waveguide modes.To simplify the optimization process,the scattering matrix(S-matrix)of the crossover is calculated.Two prototypes loaded and unloaded electromagnetic band gap(EBG)are fabricated and measured.The electrical contact problem at assembly plane is eliminated by the prototype loaded EBG.A measured bandwidth of 17.3%from 92.5 to 110 GHz for reflection and isolation coefficients<-15 dB and transmission coefficient>-2 dB is achieved.展开更多
A new dual-polarized staggered and stacked patches antenna with wide impedance band-width and high isolation is proposed.The antenna consists of two groups of radiation patches,in 7 layers,and uses the orthogonal adja...A new dual-polarized staggered and stacked patches antenna with wide impedance band-width and high isolation is proposed.The antenna consists of two groups of radiation patches,in 7 layers,and uses the orthogonal adjacent coupling structure on staggered layer to excite a pair of linear polarization modes.Thanks to the staggered feeder mode,it has increased the isolation performance be-tween ports and compressed the transverse size of the antenna.As a result of the combination of staggered stack-up between the patches and the stepped gradient shape of the main radiating patches,it has effectively expanded the impedance bandwidth of the antenna.The proposed antenna is simulated,fabricated and measured.The staggered feeding structure effectively reduces the cross-sectional area of the antenna,and greatly improves the isolation between feeding ports.The measurement results show that the impedance bandwidths for vertical and horizontal polarization modes are 40.2%(638-960 MHz)and 40.0%(645-968 MHz)respectively when the return loss is lower than-10 dB,and the isolation between feeding ports is better than-30 dB.Meanwhile,the antenna has a stable and symmetrical radiation pattern across the working band,therefore making it suitable to be used as antenna and antenna array element of mobile wireless communication base stations.展开更多
To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation c...To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation control of high dams and its numerical simulation method,and theoretical description of the complicated dynamics problem of the tri-phase coupling-thermodynamics state-material-contact bi-nonlinearity,as well as the simulation analysis of the key effects of dynamic catastrophe of the air-cushion isolated high dam engineering.The analytic solution of plane-wave with rigid-dam body was created.The simulation comparison of dynamic catastrophe processes of 305 m Jinping arch dam with and without seismic control was carried out,and the results were basically in agreement with that obtained from the large shaking table tests,and verify each other.The entire air-chamber and optimized air-cushion with varying thickness were presented to develop a optimization method.The large shaking table tests of the isolated dam model,which is satisfied with the basic dynamic similarity relations,were performed for the first time.The test data seemed to be convincing and were in agreement with the dynamic simulation results of the tested model,thereby providing an experimental verification to the simulation theory and method.The combination experiments of theoretical model and physical model demonstrated that the hydrodynamic pressure of high arch dams can be reduced by more than 70% as well as the first and third principle stresses of the dam body reduced by more than 20%-30%,thereby the global anti-seismic capacity of the high dam being improved significantly.The results have shown that the air-cushion isolation is the prior developing direction of structural control technology of high concrete dams.展开更多
Background: Methicillin-resistant Staphylococcus aureus (MRSA) are pathogens that have major negative impact in all aspects of patient care and are increasingly being recognized as troublesome pathogens in the communi...Background: Methicillin-resistant Staphylococcus aureus (MRSA) are pathogens that have major negative impact in all aspects of patient care and are increasingly being recognized as troublesome pathogens in the community. The MRSA are multi-drug resistant bacteria responsible for higher morbidity, mortality and cost of treatment in the affected patients. Research on MRSA antimicrobial susceptibility and resistance in developing countries is limited;hence accurate burden is not certain. Objective: To determine the prevalence and susceptibility pattern of MRSA in S. aureus isolates from patients treated in various units at Moi Teaching and Referral Hospital. Study Design: Cross-sectional design was used to conduct the study. Methods and Materials: Staphylococcus aureus stored isolates from patients at various units at Moi Teaching and Referral Hospital (MTRH) were identified by laboratory conventional methods. Methicillin resistant Staphylococcus aureus was determined using cefoxitin and oxacillin, discs and confirmed by Penicillin Binding Protein (PBP2a’) latex agglutination test. Susceptibility testing was performed according to the Clinical Laboratory Standards Institute procedures. Control strains used were: ATCC 43300 for Methicillin resistant S. aureus (MRSA) strains and ATCC 29213 for methicillin susceptible S. aureus (MSSA) strains. Nine anti-microbials (Erythromycin, Gentamycin, Tetracycline, Vancomycin, Rifampin, Linezolid, Ciprofloxacin, Clindamycin and Fucidicacid) were used to test the anti-microbial susceptibility patterns. Control organisms were run along with the isolates for quality Assurance. The data was analyzed using STATA version 11. Categorical variables were summarized as frequencies and the corresponding percentages. Results were presented using tables and graphs. Results: A total of 107 isolates of S. aureus were obtained, of which 39 (37%) were MRSA. Most of the MRSA, 13 (33%) and 7 (17%), were found in pus and tracheal aspirate samples respectively. Majority of the MRSA isolates were from surgical wards and intensive care unit. The MRSA isolates were highly resistant to erythromycin (92%;36/39) and tetracycline (92% 36/39) and moderately susceptible to linezolid (77% 30/39), Vancomycin (75% 29/39) and fucidic acid (67% 26/39). A total of 28 (74.4%) MRSA isolates were Clindamycin inducible resistant. Conclusions and Recommendations: This study showed that MRSA is a significant pathogen at MTRH. The MRSA were most detected in pus specimens and least in peritoneal aspirates. Routine Screening of S. aureus isolates for MRSA strains at MTRH is therefore imperative. Infection control measures should be put in place to reduce prevalence and prevent the spread of MRSA at MTRH.展开更多
This paper presents a new ZVT （zero-voltage transition） single-stage ac-to-dc converter using PWM （pulse width modulation） and HF （high frequency） transformer isolation with capacitive output filter. In this con...This paper presents a new ZVT （zero-voltage transition） single-stage ac-to-dc converter using PWM （pulse width modulation） and HF （high frequency） transformer isolation with capacitive output filter. In this converter a front-end power factor corrected boost stage integrates with a cascaded dc-to-dc bridge HF converter. The front-end boost converter operates in discontinuous current mode and ensures natural power factor correction with very simple control. The auxiliary circuit of this topology deals with very small power and is placed out of the main power path. As a result, the auxiliary circuit components have smaller power rating as opposed to main converter components. Also, output rectifier voltage is clamped to output voltage due to capacitive output filter. Identification and analyses of different operating modes of this converter are presented. Based on these analyses design example of a 50 kHz, 48 V, 1 kW ac-to-dc converter is presented. PSPICE simulation results of the designed converter are presented and explained to verify the performance of this converter.展开更多
PREPARATION of HMW DNA (Megabase-size) is the basis for construction of genomic library with large DNA inserts such as bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC), and for long-range ph...PREPARATION of HMW DNA (Megabase-size) is the basis for construction of genomic library with large DNA inserts such as bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC), and for long-range physical mapping. It can also be used for the macro-study of repeat sequences. Since HMW DNA during preparation is inclined to be sheared physically and digested by internal nucleases, it is very difficult to prepare the HMW DNA. Initially, plant HMW DNA was prepared by embedding protoplasts in the low melting-point (LMP) agarose; however, it had several disadvantages: (ⅰ) Culture of protoplasts was time-consuming, costly and tedious. ( ⅱ ) It was only used successfully for limited展开更多
A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedan...A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced （within 0.5 dB） power splitting and consistent （±5°） phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios （SWRs） of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation （〉 45 dB） and cross polarization （〉 30 dB） over the entire operating frequency band. Moreover, the gain （-8.6 dB） of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system （DCS）, personal communications service （PCS） and 3rd generation （3G） applications.展开更多
The transmision mechanism of vibrational power flow in the complex flekible coupled system of machinery mouned on a multi-storey plant building via isolators are studied in this paper from the viewpoint of energy. In ...The transmision mechanism of vibrational power flow in the complex flekible coupled system of machinery mouned on a multi-storey plant building via isolators are studied in this paper from the viewpoint of energy. In view of practical isolation designs in engineering,an asymmetric isolation system with mtiltiple isolators on a fiekible foundation is modeled, in which the interactions between the machine and the floor, and among different mouating points are taken illto account. Moreover, the transmission characteristics of power flow in the system concerned are analyzed with the use of subsystem mobility synthetic techaique. Further more,the power flow spectra of the asymmetric system are calculated and compared with those of symmetric one to reveal the effects of asymmetricity and system parameters on the power flow.Finally, new approaches to the control of structural vibration and acoustics for this kin of problems are proposed.展开更多
基金supported by National Natural Science Foundations of China (No.61422103, and No.61671084)National Key Basic Research Program of China (973 Program) (No.2014CB339900)BUPT Excellent Ph.D. Students Foundation (CX2016303)
文摘A planar circuit structure, which is based on three cascaded pairs of coupled lines, an open stub, and an isolation resistor, is proposed in this paper to design a compact dual.band balun with high isolation. This circuit features equal power division with out of phase, all ports matching, high isolation between two outputs, compact structure, and inherent impedance transformation. The closedform design equations are derived based on the traditional transmission.line theory and even.(odd.) mode analysis. A practical dual.band balun, which operates at 0.9/1.8GHz, is designed and fabricated to validate the function of equal power division with out of phase and high isolation between two outputs. The consistency between the simulated and measured results verify the design theory.
文摘To solve the safe horizontal transportation by rail&road of remote sensing satellite problem in the process of unpredictable dynamic load,a high attenuation vibration isolation damper(hereinafter referred to as vibration isolation damper)was developed.By simulation analysis and transportation test using satellite structural model and engineering prototype,validity and reliability of the vibration isolation damper was verified,which can meet the requirements of vibration and shock from various transportation conditions.
基金Project(2015-GX-108A)supported by Qinghai Provincial Science and Technology Support Program,China
文摘The bottleneck of strontium compounds preparing from celestite is the promotion of Sr/S isolation efficiency.Low energy consumption and zero release method for isolating Sr/S in preparing Sr(OH)2 process from celestite in mild condition was described.Sr element remained in precipitation with formation of Sr(OH)2,while S element entered into leachate with formation of Na2SO4.The effects of initial concentration of NaOH,conversion temperature,liquid-to-solid(L/S)ratio and conversion time on Sr/S ratio of samples for celestite conversion were systematically investigated by experiments.The results demonstrated that the efficiency of Sr/S isolation increased with the initial concentration of NaOH,L/S ratio and conversion time,and decreased with conversion temperature.The maximum conversion ratio of Sr(OH)2 was 93.88%under the optimum condition,whose Sr/S ratio of sample could reach to 41.16.It illustrated that better isolation efficiency of celestite could be achieved in alkaline treatment.The results of SEM-EDS analyses demonstrated that the conversion reaction was a dissolution-precipitation process.
文摘High affinity phosphate transporterplays an important role in plantadapting to low phosphorus. Isolationof genes coding this kind of proteinhas attracted worldwide scholars toaccomplish. We aimed to isolate thegene and transfer it to target plants
基金supported by the National Natural Science Foundations of China (61771435)
文摘In this paper, a co-polarized, co-located electric and magnetic dipoles(CCEMD) with high isolation is presented. The antenna consists of a loop based on segmented line and two independent feeding ports. Two modes of the antenna are exited separately, the first one has a radiation pattern equivalent to an electric dipole by exciting anti-phase current with symmetric distribution, and the second one is like a magnetic dipole by exciting uniform and in-phase currents along the loop. The antenna is fabricated and tested. Its measured common-10 d B impedance bandwidth at two ports is 280 MHz(2.32-2.6 GHz) with isolation better than 41 d B. Its MIMO performance in terms of capacity gain(CG) over the SISO system is investigated in a multipath rich environment containing two parallel PEC planes by both measurements and image theory based simulations. Results show that, in free space, the CG results are just slightly larger than 1, however, in the multipath rich channel, the CG values are very close to 2, which indicates that two separate subchannels can be achieved by the proposed CCEMD. The measured results of CG agree well with that obtained by simulation.
基金supported in part by the funding from the National Natural Scientific Foundation(81370518)the National High Technology Research and Development Program of China(2015AA020924 and 2013ZX10004003)supported by a grant from the Beijing Nova Program(No.Z141107001814054)
文摘The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.
基金the National Natural Science Foundation of China under Grant No.61474112 and Grant No.62001039.
文摘In this paper,a new approach to design terahertz(THz)E-plane crossover coupler is reported.By cascading two symmetrical septum polarizers,a simple structure with wide operating bandwidth and high isolation performance is achieved.The working principle is explained by operating waveguide modes.To simplify the optimization process,the scattering matrix(S-matrix)of the crossover is calculated.Two prototypes loaded and unloaded electromagnetic band gap(EBG)are fabricated and measured.The electrical contact problem at assembly plane is eliminated by the prototype loaded EBG.A measured bandwidth of 17.3%from 92.5 to 110 GHz for reflection and isolation coefficients<-15 dB and transmission coefficient>-2 dB is achieved.
基金Natural Science Founda-tion of China(Grant 61171051 and 61771063)Plan-ning projects of Hebei provincial department(Grant 15210410)Research Fund Project of North China Institute of Aerospace Engineering(Grant BKY-2021-13)。
文摘A new dual-polarized staggered and stacked patches antenna with wide impedance band-width and high isolation is proposed.The antenna consists of two groups of radiation patches,in 7 layers,and uses the orthogonal adjacent coupling structure on staggered layer to excite a pair of linear polarization modes.Thanks to the staggered feeder mode,it has increased the isolation performance be-tween ports and compressed the transverse size of the antenna.As a result of the combination of staggered stack-up between the patches and the stepped gradient shape of the main radiating patches,it has effectively expanded the impedance bandwidth of the antenna.The proposed antenna is simulated,fabricated and measured.The staggered feeding structure effectively reduces the cross-sectional area of the antenna,and greatly improves the isolation between feeding ports.The measurement results show that the impedance bandwidths for vertical and horizontal polarization modes are 40.2%(638-960 MHz)and 40.0%(645-968 MHz)respectively when the return loss is lower than-10 dB,and the isolation between feeding ports is better than-30 dB.Meanwhile,the antenna has a stable and symmetrical radiation pattern across the working band,therefore making it suitable to be used as antenna and antenna array element of mobile wireless communication base stations.
基金supported by the National Natural Science Foundation of China (Grant No. 90715026)
文摘To focus on the key scientific problem of process control of dynamic catastrophe of high dams,presented for the first time are the modelling theory of liquid-gas-solid tri-phase coupling of the air-cushion isolation control of high dams and its numerical simulation method,and theoretical description of the complicated dynamics problem of the tri-phase coupling-thermodynamics state-material-contact bi-nonlinearity,as well as the simulation analysis of the key effects of dynamic catastrophe of the air-cushion isolated high dam engineering.The analytic solution of plane-wave with rigid-dam body was created.The simulation comparison of dynamic catastrophe processes of 305 m Jinping arch dam with and without seismic control was carried out,and the results were basically in agreement with that obtained from the large shaking table tests,and verify each other.The entire air-chamber and optimized air-cushion with varying thickness were presented to develop a optimization method.The large shaking table tests of the isolated dam model,which is satisfied with the basic dynamic similarity relations,were performed for the first time.The test data seemed to be convincing and were in agreement with the dynamic simulation results of the tested model,thereby providing an experimental verification to the simulation theory and method.The combination experiments of theoretical model and physical model demonstrated that the hydrodynamic pressure of high arch dams can be reduced by more than 70% as well as the first and third principle stresses of the dam body reduced by more than 20%-30%,thereby the global anti-seismic capacity of the high dam being improved significantly.The results have shown that the air-cushion isolation is the prior developing direction of structural control technology of high concrete dams.
文摘Background: Methicillin-resistant Staphylococcus aureus (MRSA) are pathogens that have major negative impact in all aspects of patient care and are increasingly being recognized as troublesome pathogens in the community. The MRSA are multi-drug resistant bacteria responsible for higher morbidity, mortality and cost of treatment in the affected patients. Research on MRSA antimicrobial susceptibility and resistance in developing countries is limited;hence accurate burden is not certain. Objective: To determine the prevalence and susceptibility pattern of MRSA in S. aureus isolates from patients treated in various units at Moi Teaching and Referral Hospital. Study Design: Cross-sectional design was used to conduct the study. Methods and Materials: Staphylococcus aureus stored isolates from patients at various units at Moi Teaching and Referral Hospital (MTRH) were identified by laboratory conventional methods. Methicillin resistant Staphylococcus aureus was determined using cefoxitin and oxacillin, discs and confirmed by Penicillin Binding Protein (PBP2a’) latex agglutination test. Susceptibility testing was performed according to the Clinical Laboratory Standards Institute procedures. Control strains used were: ATCC 43300 for Methicillin resistant S. aureus (MRSA) strains and ATCC 29213 for methicillin susceptible S. aureus (MSSA) strains. Nine anti-microbials (Erythromycin, Gentamycin, Tetracycline, Vancomycin, Rifampin, Linezolid, Ciprofloxacin, Clindamycin and Fucidicacid) were used to test the anti-microbial susceptibility patterns. Control organisms were run along with the isolates for quality Assurance. The data was analyzed using STATA version 11. Categorical variables were summarized as frequencies and the corresponding percentages. Results were presented using tables and graphs. Results: A total of 107 isolates of S. aureus were obtained, of which 39 (37%) were MRSA. Most of the MRSA, 13 (33%) and 7 (17%), were found in pus and tracheal aspirate samples respectively. Majority of the MRSA isolates were from surgical wards and intensive care unit. The MRSA isolates were highly resistant to erythromycin (92%;36/39) and tetracycline (92% 36/39) and moderately susceptible to linezolid (77% 30/39), Vancomycin (75% 29/39) and fucidic acid (67% 26/39). A total of 28 (74.4%) MRSA isolates were Clindamycin inducible resistant. Conclusions and Recommendations: This study showed that MRSA is a significant pathogen at MTRH. The MRSA were most detected in pus specimens and least in peritoneal aspirates. Routine Screening of S. aureus isolates for MRSA strains at MTRH is therefore imperative. Infection control measures should be put in place to reduce prevalence and prevent the spread of MRSA at MTRH.
文摘This paper presents a new ZVT （zero-voltage transition） single-stage ac-to-dc converter using PWM （pulse width modulation） and HF （high frequency） transformer isolation with capacitive output filter. In this converter a front-end power factor corrected boost stage integrates with a cascaded dc-to-dc bridge HF converter. The front-end boost converter operates in discontinuous current mode and ensures natural power factor correction with very simple control. The auxiliary circuit of this topology deals with very small power and is placed out of the main power path. As a result, the auxiliary circuit components have smaller power rating as opposed to main converter components. Also, output rectifier voltage is clamped to output voltage due to capacitive output filter. Identification and analyses of different operating modes of this converter are presented. Based on these analyses design example of a 50 kHz, 48 V, 1 kW ac-to-dc converter is presented. PSPICE simulation results of the designed converter are presented and explained to verify the performance of this converter.
文摘PREPARATION of HMW DNA (Megabase-size) is the basis for construction of genomic library with large DNA inserts such as bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC), and for long-range physical mapping. It can also be used for the macro-study of repeat sequences. Since HMW DNA during preparation is inclined to be sheared physically and digested by internal nucleases, it is very difficult to prepare the HMW DNA. Initially, plant HMW DNA was prepared by embedding protoplasts in the low melting-point (LMP) agarose; however, it had several disadvantages: (ⅰ) Culture of protoplasts was time-consuming, costly and tedious. ( ⅱ ) It was only used successfully for limited
基金supported by the National Natural Science Foundation of China (61301032)
文摘A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced （within 0.5 dB） power splitting and consistent （±5°） phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios （SWRs） of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation （〉 45 dB） and cross polarization （〉 30 dB） over the entire operating frequency band. Moreover, the gain （-8.6 dB） of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system （DCS）, personal communications service （PCS） and 3rd generation （3G） applications.
文摘The transmision mechanism of vibrational power flow in the complex flekible coupled system of machinery mouned on a multi-storey plant building via isolators are studied in this paper from the viewpoint of energy. In view of practical isolation designs in engineering,an asymmetric isolation system with mtiltiple isolators on a fiekible foundation is modeled, in which the interactions between the machine and the floor, and among different mouating points are taken illto account. Moreover, the transmission characteristics of power flow in the system concerned are analyzed with the use of subsystem mobility synthetic techaique. Further more,the power flow spectra of the asymmetric system are calculated and compared with those of symmetric one to reveal the effects of asymmetricity and system parameters on the power flow.Finally, new approaches to the control of structural vibration and acoustics for this kin of problems are proposed.
