A high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave(CW) and acousto–optical(A-O) Q-switched operation is demonstrated in this work. A symmetrically shaped flat–flat cavity with two identi...A high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave(CW) and acousto–optical(A-O) Q-switched operation is demonstrated in this work. A symmetrically shaped flat–flat cavity with two identical LEDside-pumped laser modules is employed for power scalability. In the CW regime, the maximum output average power of laser at 1064 nm is 4.41 W, corresponding to a maximum optical conversion efficiency of 5.3% and a slope efficiency is 12.4%. In the active Q-switched regime, the pulse energy of laser reaches as high as 0.89 m J at a repetition rate of 800 Hz with a pulse width of 457.2 ns, the corresponding highest peak output power is 1.94 k W and the M~2 factor is measured to be about 8.8. To the best of the authors' knowledge, this is the first demonstration and the highest performance of a CW LED-side-pumped two-rod laser Nd,Ce:YAG with Watt-level output reported so far.展开更多
A diode-pumped actively Q-switched Raman laser is demonstrated, with YV04 employed as Raman active medium, based on a ceramic Nd：YAG laser operating at 1444nm. The first-stokes Raman generation at 1657nm is achieved....A diode-pumped actively Q-switched Raman laser is demonstrated, with YV04 employed as Raman active medium, based on a ceramic Nd：YAG laser operating at 1444nm. The first-stokes Raman generation at 1657nm is achieved. A maximum output power of as high as 612mW is obtained under a pump power of 20. 7 W and at a pulse repetition frequency rate of 20kHz, corresponding to an optical-to-optical conversion efficiency of 3%.展开更多
The paper analyzes the financing activity, investing activity and operating activity of Target Corporation by comparing with other companies in the same industry. The analysis shows that Target overall is better at me...The paper analyzes the financing activity, investing activity and operating activity of Target Corporation by comparing with other companies in the same industry. The analysis shows that Target overall is better at meeting it in short-term obligations as well as earning money for its investors. Target is a safe and consistent investment. The company should pay attention to interest rate changes because the company＇s majority of financing charges are based on floating-rate debt obligations.展开更多
The accounting information should help investors and creditors evaluate the amounts, timing, and uncertainty of firms＇ future cash receipts and disbursements. The Financial Accounting Standards Board （FASB） contend...The accounting information should help investors and creditors evaluate the amounts, timing, and uncertainty of firms＇ future cash receipts and disbursements. The Financial Accounting Standards Board （FASB） contends that accrual-based historical earnings are superior to cash flows in predicting future cash flows. But, Bowen, Burgstahler, and Daley （1986） showed that traditional measures of cash flows （net income （NI） plus depreciation and working capital from operations） appear to be better predictors of future cash flows than accrual accounting earnings. Since then, many researchers have articulated the importance of accounting data, especially cash flows and NI, in the predictive and forecasting processes. In this study, we empirically re-examined the ability of cash flows from operating activities （CFO） and accrual-based NI in predicting firms＇ bankruptcy. In the past, the results of this type of research were mixed. Differently from previous research, we focus on the timing of predictive ability, i.e., which indicator, cash flows or NI, is faster in predicting a firm＇s bankruptcy. We also investigate the timing of auditors＇ issuance of a going-concern opinion. The preliminary results show that the accrual-based NI is more accurate and faster than either CFO or audit opinion in predicting firms＇ failures. On average, NI signals a firm＇s bankruptcy 2.41 years before the bankruptcy filing, while CFO signals 1.48 years before filing. Auditors issued a going-concern opinion, another signal for firms＇ failure, to only 16 out of 41 bankrupt firms one year before bankruptcy, and no auditor issued the going-concern opinion two years before bankruptcy.展开更多
Pulse width modulated current-source converter(PWM-CSC)has great prospects in high voltage direct current transmission system(HVDC)due to its attractive features,such as flexible control characteristics,ability to avo...Pulse width modulated current-source converter(PWM-CSC)has great prospects in high voltage direct current transmission system(HVDC)due to its attractive features,such as flexible control characteristics,ability to avoid commutation failure,and lower cost.However,valve voltage of the PWM-CSC is the jump value between filter capacitors line-voltage and zero voltage due to its bypass operation,resulting in high peak voltage withstand by the converter for a rated HVDC system and high voltage ripper ratio.In order to solve these issues,an improved modulation method called specific carrier frequency of SPWM is proposed.After adopting the improved modulation method,the number of the reverse blocking integrated gate commutated thyristor(RB-IGCT)in series can reduce by 31.5%under unity power factor operation and the value of the dc choke can reduce by about 78.6%compared to traditional modulation methods,improving practicability of engineering application.Moreover,active power and reactive power operating range are derived under different modulation methods and the relationship of the power factor,modulation in q-axis and DC current are studied.Finally,effectiveness of the improved modulation method and comparisons of power operating range are verified in PSCAD/EMTDC.展开更多
基金Project supported by the Fund from Nanjing University of Posts and Telecommunications,China(Grant Nos.JUH219002 and JUH219007)the Key Research and Development Program of Shandong Province,China(Grant No.2021CXGC010202)。
文摘A high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave(CW) and acousto–optical(A-O) Q-switched operation is demonstrated in this work. A symmetrically shaped flat–flat cavity with two identical LEDside-pumped laser modules is employed for power scalability. In the CW regime, the maximum output average power of laser at 1064 nm is 4.41 W, corresponding to a maximum optical conversion efficiency of 5.3% and a slope efficiency is 12.4%. In the active Q-switched regime, the pulse energy of laser reaches as high as 0.89 m J at a repetition rate of 800 Hz with a pulse width of 457.2 ns, the corresponding highest peak output power is 1.94 k W and the M~2 factor is measured to be about 8.8. To the best of the authors' knowledge, this is the first demonstration and the highest performance of a CW LED-side-pumped two-rod laser Nd,Ce:YAG with Watt-level output reported so far.
基金Supported by the Foundation of the State Key Laboratory of Crystal Material of Shandong University under Grant No KF1101the Foundation of Shandong University under Grant No 1170072613176+2 种基金the National Natural Science Foundation of China under Grant Nos 11004122 and 11204160the Special Grade of China Postdoctoral Science Foundation under Grant No 201104627the Independent Innovation Foundation of Shandong University under Grant No 2011GN058
文摘A diode-pumped actively Q-switched Raman laser is demonstrated, with YV04 employed as Raman active medium, based on a ceramic Nd：YAG laser operating at 1444nm. The first-stokes Raman generation at 1657nm is achieved. A maximum output power of as high as 612mW is obtained under a pump power of 20. 7 W and at a pulse repetition frequency rate of 20kHz, corresponding to an optical-to-optical conversion efficiency of 3%.
文摘The paper analyzes the financing activity, investing activity and operating activity of Target Corporation by comparing with other companies in the same industry. The analysis shows that Target overall is better at meeting it in short-term obligations as well as earning money for its investors. Target is a safe and consistent investment. The company should pay attention to interest rate changes because the company＇s majority of financing charges are based on floating-rate debt obligations.
文摘The accounting information should help investors and creditors evaluate the amounts, timing, and uncertainty of firms＇ future cash receipts and disbursements. The Financial Accounting Standards Board （FASB） contends that accrual-based historical earnings are superior to cash flows in predicting future cash flows. But, Bowen, Burgstahler, and Daley （1986） showed that traditional measures of cash flows （net income （NI） plus depreciation and working capital from operations） appear to be better predictors of future cash flows than accrual accounting earnings. Since then, many researchers have articulated the importance of accounting data, especially cash flows and NI, in the predictive and forecasting processes. In this study, we empirically re-examined the ability of cash flows from operating activities （CFO） and accrual-based NI in predicting firms＇ bankruptcy. In the past, the results of this type of research were mixed. Differently from previous research, we focus on the timing of predictive ability, i.e., which indicator, cash flows or NI, is faster in predicting a firm＇s bankruptcy. We also investigate the timing of auditors＇ issuance of a going-concern opinion. The preliminary results show that the accrual-based NI is more accurate and faster than either CFO or audit opinion in predicting firms＇ failures. On average, NI signals a firm＇s bankruptcy 2.41 years before the bankruptcy filing, while CFO signals 1.48 years before filing. Auditors issued a going-concern opinion, another signal for firms＇ failure, to only 16 out of 41 bankrupt firms one year before bankruptcy, and no auditor issued the going-concern opinion two years before bankruptcy.
基金supported in part by Science and Technology Project of State Grid Corporation of China(5500202058059A0000).
文摘Pulse width modulated current-source converter(PWM-CSC)has great prospects in high voltage direct current transmission system(HVDC)due to its attractive features,such as flexible control characteristics,ability to avoid commutation failure,and lower cost.However,valve voltage of the PWM-CSC is the jump value between filter capacitors line-voltage and zero voltage due to its bypass operation,resulting in high peak voltage withstand by the converter for a rated HVDC system and high voltage ripper ratio.In order to solve these issues,an improved modulation method called specific carrier frequency of SPWM is proposed.After adopting the improved modulation method,the number of the reverse blocking integrated gate commutated thyristor(RB-IGCT)in series can reduce by 31.5%under unity power factor operation and the value of the dc choke can reduce by about 78.6%compared to traditional modulation methods,improving practicability of engineering application.Moreover,active power and reactive power operating range are derived under different modulation methods and the relationship of the power factor,modulation in q-axis and DC current are studied.Finally,effectiveness of the improved modulation method and comparisons of power operating range are verified in PSCAD/EMTDC.
