To overcome vendor lock-in obstacles in public cloud computing, the capability to define transferable cloud-based services is crucial but has not yet been solved satisfactorily. This is especially true for small and m...To overcome vendor lock-in obstacles in public cloud computing, the capability to define transferable cloud-based services is crucial but has not yet been solved satisfactorily. This is especially true for small and medium sized enterprises being typically not able to operate a vast staff of cloud service and IT experts. Actual state of the art cloud service design does not systematically deal with how to define, deploy and operate cross-platform capable cloud services. This is mainly due to inherent complexity of the field and differences in details between a plenty of existing public and private cloud infrastructures. One way to handle this complexity is to restrict cloud service design to a common subset of commodity features provided by existing public and private cloud infrastructures. Nevertheless these restrictions raise new service design questions and have to be answered in ongoing research in a pragmatic manner regarding the limited IT-operation capabilities of small and medium sized enterprises. By simplifying and harmonizing the use of cloud infrastructures using lightweight virtualization approaches, the transfer of cloud deployments between a variety of cloud service providers will become possible. This article will discuss several aspects like high availability, secure communication, elastic service design, transferability of services and formal descriptions of service deployments which have to be addressed and are investigated by our ongoing research.展开更多
Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions i...Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.展开更多
In order to make the supply chain select the best emergency procurement suppliers in case the procurement system encounters unexpected risks,six indices which can reflect the comprehensive abilities of alternative sup...In order to make the supply chain select the best emergency procurement suppliers in case the procurement system encounters unexpected risks,six indices which can reflect the comprehensive abilities of alternative suppliers are selected,i.e.,the product yield,the toll standard,the on-time-delivery rate,the rate of turnover industry experience and customer satisfaction.Then standardized processing of evaluation is performed.For quantitative indices,vector normalization is adopted to perform standardized processing,and qualitative fuzziness indices are quantified through assignment.Finally,each index can be transformed into a standardized mark which has dimensionless 1 and the same magnitude.And an expert method is used to determine the index weights and then the linear weighted sum method is used to calculate the alternative supplier's comprehensive ability score and by comparing these scores,the optimal emergency procurement supplier is selected.展开更多
By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, construc...By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, constructs a VMI mathematics model, and analyzes the influence of VMI on inventory cost and channel profit. Finally, a special case is studied to verify that VMI is an effective supply chain strategy that can not only increase channel profit of supplier and customer but also improve full channel coordination, thereby reducing the bullwhip effect.展开更多
This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple ...This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple exponentially weighted moving average. It also examines a vendor managed inventory (VMI) program to determine how it can help alleviate such negative effects, and gives the theoretical proofs and numerical illustrations. The results show that the effects with VMI are better than the effect without VMI in demand forecasting and safety stock levels, etc.展开更多
In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consoli...In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.展开更多
The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, havi...The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, having initial stock and having stock-out cost. With the further analysis of the mode, VMI is found to increase profits of the buyer in the short-term motivation. But VMI will reduce profits of the supplier under the matching condition. And in the short-term motivation, VMI will increase the purchase price to compensate the transfer cost of the supplier. As a result, the foundation of theory is provided to implement VMI in the supply chain, and have some definituded project significance.展开更多
Numerical simulations are performed to study the aeroelastic responses of an elastically suspended airfoil in transonic buffet flow, by coupling the unsteady Reynolds-averaged Navier- Stokes （RANS） equations and str...Numerical simulations are performed to study the aeroelastic responses of an elastically suspended airfoil in transonic buffet flow, by coupling the unsteady Reynolds-averaged Navier- Stokes （RANS） equations and structural motion equation. The current work focuses on the char- acteristic analysis of the lock-in phenomenon. Great attentions are paid to studying the frequency range of lock-in and the effects of the three parameters, namely the structural natural frequency, mass ratio and structural damping, on lock-in characteristic of the elastic system in detail. It is found that when the structural natural frequency is close to the buffet frequency, the coupling fre- quency of the elastic system is no longer equal to the buffet frequency, but keeps the same value as the structural natural frequency. The frequency lock-in occurs and stays present until the structural nature frequency is near the double buffet frequency. It means that the lock-in presents within a broad range, of which the lower threshold is near the buffet frequency, while the upper threshold is near the double buffet frequency. Moreover, the frequency range of lock-in is affected by mass ratio and structural damping. The lower the mass ratio and structural damping are, the wider the range of lock-in will be. The upper threshold of lock-in grows with the mass ratio and structural damping decreasing, but the lower threshold always keeps the same.展开更多
In this study,the lock-in phenomenon of Tip Clearance Flow(TCF)instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance.The capabiliti...In this study,the lock-in phenomenon of Tip Clearance Flow(TCF)instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance.The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data,respectively.The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency.The lock-in region becomes wider with the vibration amplitude increasing,and it is also affected by modal shapes.For the rotor at the simulation conditions in this study,the bending mode results in a wider lock-in region than the torsional mode.In the lock-in region,the phase difference between the Tip Clearance Vortex(TCV)and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities.The frequency of the TCV instabilities reduces with the mass flow decreasing.Therefore,reducing mass flow and increasing frequency ratio have similar effects on the TCV phase,which causes a significant variation on the unsteady pressure amplitude in the blade tip area.Thus,the aerodynamic damping changes significantly with the TCV phase.The aerodynamic damping displays a nonlinear relationship with the vibration amplitude,and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio.The negative damping is mainly provided by the tip area of the blade.For unlocked conditions,the period of the TCF instabilities fluctuates over time,and it cannot be directly separated by their frequency features.Inter Blade Phase Angle(IBPA)also has an important influence on the feature of the TCV instabilities.The occurrence of frequency lock-in also requires“appropriate”IBPA.For the examined working conditions,the frequency lock-in occurs under 0 ND(Nodal Diameter),but not under 8 ND.However,no matter 0 ND or 8 ND,the phase of TCV always locks onto the IBPA at the examined conditions.展开更多
Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air po...Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air pollution. The study determined the prevalence of allergic rhinitis and its associated risk factors in these vendors. Methods: This was a cross-sectional survey based on a structured questionnaire, conducted among vendors in the neighborhoods of HLM, Medina and Petersen in Dakar, Senegal. A total of 200 vendors were interviewed. Symptoms of allergic rhinitis were defined as the simultaneous presence of rhinorrhea, nasal congestion and sneezing in the absence of respiratory infection. A logistic regression analysis was performed to determine the relationship between socio-demographic characteristics, occupational factors, and allergic rhinitis. Results: Results of the study show a prevalence of 43% of allergic rhinitis among vendors. Multivariate analysis showed that the independent factors associated with allergic rhinitis in these vendors were age [OR: 3.28 (1.02 - 10.51)], working area [OR: 8.31 (2.39 - 28.95)], exposure to multiple sources of pollution [OR: 4.08 (1.43 - 11.63)], and recurrent cold [OR: 4.39 (1.15 - 16.85)]. Conclusion: The prevalence of allergic rhinitis was high among vendors in Dakar. Our data suggest that exposure to air pollution at the workplace in vendors could lead to allergic rhinitis.展开更多
Introduction: Musculoskeletal disorders (MSDs) are a set of peri-articular conditions that result mainly in pain and functional discomfort. They represent a major occupational health problem in all areas of activity. ...Introduction: Musculoskeletal disorders (MSDs) are a set of peri-articular conditions that result mainly in pain and functional discomfort. They represent a major occupational health problem in all areas of activity. The objective of this work was to determine the prevalence of MSDs among street vendors in the city of Bangui in the Central African Republic (CAR). Methods: A cross-sectional study was conducted from September 01 to October 31, 2021 in Bangui, the capital of CAR. The study population consisted of street vendors which were included at the entrance of 4 large markets of Bangui after giving informed consent. The sample size, calculated according to the Schwartz formula, was 384. Sociodemographic data (age, gender, level of education, marital status), professional data (the duration of sale in hours, the distance traveled per day);and health data (the health problems suffered by itinerant sellers and the means of dealing with them) were collected using a pre-established self-questionnaire. This collected data was processed using Microsoft Excel 2013 and Epi-Info version 7 software. Results: Among 384 street vendors included, women represented a quarter (24.9%). The average age was 27 years;the 25-34 age group was the most represented (50%). About two-thirds (64.8%) sold for at least 12 hours and traveled more than 10 km (69.3%) per day. The main health problems reported by street vendors were musculoskeletal disorders (95.8%). Their locations concerned the upper limbs shoulder 65.36% (251), elbow 24.22% (93). Non-ergonomic postures that stress the back and joints all day long, causing pain are risk factors for MSDs. These MSDs were treated by self-medication with non-steroidal anti-inflammatory drugs (22.0%), mainly sold on the street. Conclusion: MSDs dominated the health problems of street vendors. These problems raise the need for recognition and support for these workers to optimize their performance while preserving their health through awareness and good management of MSDs whose chronicity generates a disability.展开更多
Vendor evaluation and selection is one of the most important issues in manufacturing management.It is a multi-criteria decision problem including various factors.Traditional methods have many shortcomings.Fuzzy AHP mo...Vendor evaluation and selection is one of the most important issues in manufacturing management.It is a multi-criteria decision problem including various factors.Traditional methods have many shortcomings.Fuzzy AHP model is established to solve this problem.A general evaluation method is provided and steps are presented.As a case study,the model is implemented in an electro-mechanical product company.And a detailed example is given to illustrate the effectiveness of this approach.展开更多
The central construct of customer lock-in （CL） is measured and its role along with that of consumer loyalty in influencing the brand-customer relationship is tested. Using data collected from focus groups, a measure...The central construct of customer lock-in （CL） is measured and its role along with that of consumer loyalty in influencing the brand-customer relationship is tested. Using data collected from focus groups, a measurement model for CL is developed, and a structural equation model consisted based on literature review and our own theory is established. Moreover, the moderating effects of CL on the relationship between perceived value （PV） and brand relationship quality （BRQ） , as well as that between BRQ and brand loyalty （BL） based on data collected through a survey have been tested. Results indicate that consumer satisfaction is a critical factor in establishing brand-customer relationship, and the attitudinal brand loyalty is the key to obtain brand behavioral loyalty. Furthermore, CL tactics, such as decreasing consumers＇ learning cost and transactional cost facilitate the relationship building between customer and brand, while involuntary lock-in may have an adverse effect in the relationship building process. In addition, involuntary lock-in and loyalty program help in obtaining consumers＇ behavioral brand loyalty but not their attitudinal loyalty.展开更多
In the novel prototype of micro-gyroscope structure,the new configured capacitance sensing scheme for the micro gyroscope was analyzed and the virtual instrument based detection scheme was implemented.The digital lock...In the novel prototype of micro-gyroscope structure,the new configured capacitance sensing scheme for the micro gyroscope was analyzed and the virtual instrument based detection scheme was implemented.The digital lock-in amplifier was employed in the capacitance detection to restrain the noise interference.The capacitance analysis shows that 1 fF capacitance variation corresponds to 0.1 degree of the turn angle.The differential capacitance bridge and the charge integral amplifier were used as the front signal input interface.In the implementation of digital lock-in amplifier,a new routine which warranted the exactly matching of the reference phase to signal phase was proposed.The result of the experiment shows that digital lock-in amplifier can greatly eliminate the noise in the output signal.The non linearity of the turn angle output is 2.3% and the minimum resolution of turn angle is 0.04 degrees.The application of the software demodulation in the signal detection of micro-electro-mechanical-system(MEMS)device is a new attempt,and it shows the prospective for a high-performance application.展开更多
Reform and opening up has made China’s economy develop faster than ever. But it has not succeeded in changing the regional disparity in China. In this article, we establish a model factor input called the "lock-...Reform and opening up has made China’s economy develop faster than ever. But it has not succeeded in changing the regional disparity in China. In this article, we establish a model factor input called the "lock-in effect" and analyze the channel of the lock-in effect and how it influences the regional economy. On the analyses of thirty provinces’ panel data in China from 1990 to 2005, we find that the lock-in effect of factor inputs further exacerbates the developmental imbalance among regions.展开更多
Lock-in amplifiers are used to detect and measure very small alternating current(AC)signals down to the range of nVs.Accurate measurements can be made even when the small signals are buried by noise thousands of times...Lock-in amplifiers are used to detect and measure very small alternating current(AC)signals down to the range of nVs.Accurate measurements can be made even when the small signals are buried by noise thousands of times larger.With the digital signal processing(DSP)technology involved in modern instrumentation,a lock-in amplifier is more versatile in sensing and recovering small signals.Combining the virtual instrumentation technology,we reorganize the functional blocks of a programmable lock-in amplifier and build it as a virtual spectrum analyzer,virtual impedance meter,virtual network analyzer,virtual semiconductor parameter analyzer,signal generator,etc.A 4 layer model is used to implement these virtual instruments.The same virtual instrument can also be implemented on a general purpose FPGA developing board.展开更多
ZTE Corporation announced on November 10, 2011 that it has been named LTE Vendor of the Year by leading consulting firm Frost ＆ Sullivan. The Frost ＆ Sullivan LTE Vendor of the Year award is given to companies that ...ZTE Corporation announced on November 10, 2011 that it has been named LTE Vendor of the Year by leading consulting firm Frost ＆ Sullivan. The Frost ＆ Sullivan LTE Vendor of the Year award is given to companies that have achieved excellence in LTE. ZTE won the award for its growing number of secured contracts and also for its patent applications.展开更多
文摘To overcome vendor lock-in obstacles in public cloud computing, the capability to define transferable cloud-based services is crucial but has not yet been solved satisfactorily. This is especially true for small and medium sized enterprises being typically not able to operate a vast staff of cloud service and IT experts. Actual state of the art cloud service design does not systematically deal with how to define, deploy and operate cross-platform capable cloud services. This is mainly due to inherent complexity of the field and differences in details between a plenty of existing public and private cloud infrastructures. One way to handle this complexity is to restrict cloud service design to a common subset of commodity features provided by existing public and private cloud infrastructures. Nevertheless these restrictions raise new service design questions and have to be answered in ongoing research in a pragmatic manner regarding the limited IT-operation capabilities of small and medium sized enterprises. By simplifying and harmonizing the use of cloud infrastructures using lightweight virtualization approaches, the transfer of cloud deployments between a variety of cloud service providers will become possible. This article will discuss several aspects like high availability, secure communication, elastic service design, transferability of services and formal descriptions of service deployments which have to be addressed and are investigated by our ongoing research.
基金the National Natural Science Foundation of China(Nos.52171316 and 51479116)。
文摘Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.
基金The National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2006BAH02A06)
文摘In order to make the supply chain select the best emergency procurement suppliers in case the procurement system encounters unexpected risks,six indices which can reflect the comprehensive abilities of alternative suppliers are selected,i.e.,the product yield,the toll standard,the on-time-delivery rate,the rate of turnover industry experience and customer satisfaction.Then standardized processing of evaluation is performed.For quantitative indices,vector normalization is adopted to perform standardized processing,and qualitative fuzziness indices are quantified through assignment.Finally,each index can be transformed into a standardized mark which has dimensionless 1 and the same magnitude.And an expert method is used to determine the index weights and then the linear weighted sum method is used to calculate the alternative supplier's comprehensive ability score and by comparing these scores,the optimal emergency procurement supplier is selected.
文摘By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, constructs a VMI mathematics model, and analyzes the influence of VMI on inventory cost and channel profit. Finally, a special case is studied to verify that VMI is an effective supply chain strategy that can not only increase channel profit of supplier and customer but also improve full channel coordination, thereby reducing the bullwhip effect.
文摘This paper studies that the bullwhip effect of order releases and the amplifications of safety stock arise within the supply chain even when the demand model is ARIMA(0, 1, 1) and the forecast method used is a simple exponentially weighted moving average. It also examines a vendor managed inventory (VMI) program to determine how it can help alleviate such negative effects, and gives the theoretical proofs and numerical illustrations. The results show that the effects with VMI are better than the effect without VMI in demand forecasting and safety stock levels, etc.
基金The National Key Technology R&D Program of China during the 11 th Five-Year Plan Period(No.2006BAH02A06)
文摘In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.
文摘The optimization policy of the purchase price and the profit under vendor managed inventory(VMI) is studied. For a salable product, supply chain mode of VMI is established, which is based on deterministic demand, having initial stock and having stock-out cost. With the further analysis of the mode, VMI is found to increase profits of the buyer in the short-term motivation. But VMI will reduce profits of the supplier under the matching condition. And in the short-term motivation, VMI will increase the purchase price to compensate the transfer cost of the supplier. As a result, the foundation of theory is provided to implement VMI in the supply chain, and have some definituded project significance.
基金supported by the project of the National Natural Science Foundation of China(No.11272262)
文摘Numerical simulations are performed to study the aeroelastic responses of an elastically suspended airfoil in transonic buffet flow, by coupling the unsteady Reynolds-averaged Navier- Stokes （RANS） equations and structural motion equation. The current work focuses on the char- acteristic analysis of the lock-in phenomenon. Great attentions are paid to studying the frequency range of lock-in and the effects of the three parameters, namely the structural natural frequency, mass ratio and structural damping, on lock-in characteristic of the elastic system in detail. It is found that when the structural natural frequency is close to the buffet frequency, the coupling fre- quency of the elastic system is no longer equal to the buffet frequency, but keeps the same value as the structural natural frequency. The frequency lock-in occurs and stays present until the structural nature frequency is near the double buffet frequency. It means that the lock-in presents within a broad range, of which the lower threshold is near the buffet frequency, while the upper threshold is near the double buffet frequency. Moreover, the frequency range of lock-in is affected by mass ratio and structural damping. The lower the mass ratio and structural damping are, the wider the range of lock-in will be. The upper threshold of lock-in grows with the mass ratio and structural damping decreasing, but the lower threshold always keeps the same.
基金supported by the National Natural Science Foundation of China(No.51475022)。
文摘In this study,the lock-in phenomenon of Tip Clearance Flow(TCF)instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance.The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data,respectively.The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency.The lock-in region becomes wider with the vibration amplitude increasing,and it is also affected by modal shapes.For the rotor at the simulation conditions in this study,the bending mode results in a wider lock-in region than the torsional mode.In the lock-in region,the phase difference between the Tip Clearance Vortex(TCV)and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities.The frequency of the TCV instabilities reduces with the mass flow decreasing.Therefore,reducing mass flow and increasing frequency ratio have similar effects on the TCV phase,which causes a significant variation on the unsteady pressure amplitude in the blade tip area.Thus,the aerodynamic damping changes significantly with the TCV phase.The aerodynamic damping displays a nonlinear relationship with the vibration amplitude,and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio.The negative damping is mainly provided by the tip area of the blade.For unlocked conditions,the period of the TCF instabilities fluctuates over time,and it cannot be directly separated by their frequency features.Inter Blade Phase Angle(IBPA)also has an important influence on the feature of the TCV instabilities.The occurrence of frequency lock-in also requires“appropriate”IBPA.For the examined working conditions,the frequency lock-in occurs under 0 ND(Nodal Diameter),but not under 8 ND.However,no matter 0 ND or 8 ND,the phase of TCV always locks onto the IBPA at the examined conditions.
文摘Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air pollution. The study determined the prevalence of allergic rhinitis and its associated risk factors in these vendors. Methods: This was a cross-sectional survey based on a structured questionnaire, conducted among vendors in the neighborhoods of HLM, Medina and Petersen in Dakar, Senegal. A total of 200 vendors were interviewed. Symptoms of allergic rhinitis were defined as the simultaneous presence of rhinorrhea, nasal congestion and sneezing in the absence of respiratory infection. A logistic regression analysis was performed to determine the relationship between socio-demographic characteristics, occupational factors, and allergic rhinitis. Results: Results of the study show a prevalence of 43% of allergic rhinitis among vendors. Multivariate analysis showed that the independent factors associated with allergic rhinitis in these vendors were age [OR: 3.28 (1.02 - 10.51)], working area [OR: 8.31 (2.39 - 28.95)], exposure to multiple sources of pollution [OR: 4.08 (1.43 - 11.63)], and recurrent cold [OR: 4.39 (1.15 - 16.85)]. Conclusion: The prevalence of allergic rhinitis was high among vendors in Dakar. Our data suggest that exposure to air pollution at the workplace in vendors could lead to allergic rhinitis.
文摘Introduction: Musculoskeletal disorders (MSDs) are a set of peri-articular conditions that result mainly in pain and functional discomfort. They represent a major occupational health problem in all areas of activity. The objective of this work was to determine the prevalence of MSDs among street vendors in the city of Bangui in the Central African Republic (CAR). Methods: A cross-sectional study was conducted from September 01 to October 31, 2021 in Bangui, the capital of CAR. The study population consisted of street vendors which were included at the entrance of 4 large markets of Bangui after giving informed consent. The sample size, calculated according to the Schwartz formula, was 384. Sociodemographic data (age, gender, level of education, marital status), professional data (the duration of sale in hours, the distance traveled per day);and health data (the health problems suffered by itinerant sellers and the means of dealing with them) were collected using a pre-established self-questionnaire. This collected data was processed using Microsoft Excel 2013 and Epi-Info version 7 software. Results: Among 384 street vendors included, women represented a quarter (24.9%). The average age was 27 years;the 25-34 age group was the most represented (50%). About two-thirds (64.8%) sold for at least 12 hours and traveled more than 10 km (69.3%) per day. The main health problems reported by street vendors were musculoskeletal disorders (95.8%). Their locations concerned the upper limbs shoulder 65.36% (251), elbow 24.22% (93). Non-ergonomic postures that stress the back and joints all day long, causing pain are risk factors for MSDs. These MSDs were treated by self-medication with non-steroidal anti-inflammatory drugs (22.0%), mainly sold on the street. Conclusion: MSDs dominated the health problems of street vendors. These problems raise the need for recognition and support for these workers to optimize their performance while preserving their health through awareness and good management of MSDs whose chronicity generates a disability.
文摘Vendor evaluation and selection is one of the most important issues in manufacturing management.It is a multi-criteria decision problem including various factors.Traditional methods have many shortcomings.Fuzzy AHP model is established to solve this problem.A general evaluation method is provided and steps are presented.As a case study,the model is implemented in an electro-mechanical product company.And a detailed example is given to illustrate the effectiveness of this approach.
基金Sponsored by the National Natural Science Foundation of China (70772089)Program for New Century Excellent Talents in University (2006)
文摘The central construct of customer lock-in （CL） is measured and its role along with that of consumer loyalty in influencing the brand-customer relationship is tested. Using data collected from focus groups, a measurement model for CL is developed, and a structural equation model consisted based on literature review and our own theory is established. Moreover, the moderating effects of CL on the relationship between perceived value （PV） and brand relationship quality （BRQ） , as well as that between BRQ and brand loyalty （BL） based on data collected through a survey have been tested. Results indicate that consumer satisfaction is a critical factor in establishing brand-customer relationship, and the attitudinal brand loyalty is the key to obtain brand behavioral loyalty. Furthermore, CL tactics, such as decreasing consumers＇ learning cost and transactional cost facilitate the relationship building between customer and brand, while involuntary lock-in may have an adverse effect in the relationship building process. In addition, involuntary lock-in and loyalty program help in obtaining consumers＇ behavioral brand loyalty but not their attitudinal loyalty.
基金The National Natural Science Foundation ofChina(No.60402003)The National High Technology Research and Development Pro-gram of China(863Program)(No.2002AA745120)
文摘In the novel prototype of micro-gyroscope structure,the new configured capacitance sensing scheme for the micro gyroscope was analyzed and the virtual instrument based detection scheme was implemented.The digital lock-in amplifier was employed in the capacitance detection to restrain the noise interference.The capacitance analysis shows that 1 fF capacitance variation corresponds to 0.1 degree of the turn angle.The differential capacitance bridge and the charge integral amplifier were used as the front signal input interface.In the implementation of digital lock-in amplifier,a new routine which warranted the exactly matching of the reference phase to signal phase was proposed.The result of the experiment shows that digital lock-in amplifier can greatly eliminate the noise in the output signal.The non linearity of the turn angle output is 2.3% and the minimum resolution of turn angle is 0.04 degrees.The application of the software demodulation in the signal detection of micro-electro-mechanical-system(MEMS)device is a new attempt,and it shows the prospective for a high-performance application.
文摘Reform and opening up has made China’s economy develop faster than ever. But it has not succeeded in changing the regional disparity in China. In this article, we establish a model factor input called the "lock-in effect" and analyze the channel of the lock-in effect and how it influences the regional economy. On the analyses of thirty provinces’ panel data in China from 1990 to 2005, we find that the lock-in effect of factor inputs further exacerbates the developmental imbalance among regions.
文摘Lock-in amplifiers are used to detect and measure very small alternating current(AC)signals down to the range of nVs.Accurate measurements can be made even when the small signals are buried by noise thousands of times larger.With the digital signal processing(DSP)technology involved in modern instrumentation,a lock-in amplifier is more versatile in sensing and recovering small signals.Combining the virtual instrumentation technology,we reorganize the functional blocks of a programmable lock-in amplifier and build it as a virtual spectrum analyzer,virtual impedance meter,virtual network analyzer,virtual semiconductor parameter analyzer,signal generator,etc.A 4 layer model is used to implement these virtual instruments.The same virtual instrument can also be implemented on a general purpose FPGA developing board.
文摘ZTE Corporation announced on November 10, 2011 that it has been named LTE Vendor of the Year by leading consulting firm Frost ＆ Sullivan. The Frost ＆ Sullivan LTE Vendor of the Year award is given to companies that have achieved excellence in LTE. ZTE won the award for its growing number of secured contracts and also for its patent applications.
