This work presents a half bridge (HB) sub-modules (SMs) based modular multilevel converter (MMC) topology intended to integrate MVDC grid with single phase MVAC grid for railway traction power ...supply. The topology uses reduced arms/ chain-links (two arms) of conventional HB-MMC and a midpoint transformer at the AC side to employ galvanic isolation needed for this application. Further, by utilizing appropriate modulation technique and mid-point transformer, the cancellation of DC flux within the transformer is achieved. The inductance of the arm inductor can be combined with the leakage inductance of the mid-point transformer, thus eliminating the requirement for extra inductors. A unique pre-charging methodology for SM capacitor in the proposed topology is discussed, which differs from conventional approaches. The converter's performance during various fault scenarios is analyzed, showcasing its inherent fault blocking capability. The operational principles are explained mathematically and validated through simulations and a scaled-down experimental prototype under both normal and fault conditions.
Abstract Background The efficacy of neoadjuvant chemotherapy (NAC) for muscle-invasive bladder cancer (BCa) was established primarily with methotrexate, vinblastine, doxorubicin, and cisplatin ...(MVAC), with complete response rates (pT0) as high as 38%. However, because of the comparable efficacy with better tolerability of gemcitabine and cisplatin (GC) in patients with metastatic disease, GC has become the most commonly used regimen in the neoadjuvant setting. Objective We aimed to assess real-world pathologic response rates to NAC with different regimens in a large, multicenter cohort. Design, setting, and participants Data were collected retrospectively at 19 centers on patients with clinical cT2–4aN0M0 urothelial carcinoma of the bladder who received at least three cycles of NAC, followed by radical cystectomy (RC), between 2000 and 2013. Intervention NAC and RC. Outcome measurements and statistical analysis The primary outcome was pathologic stage at cystectomy. Univariable and multivariable analyses were used to determine factors predictive of pT0N0 and ≤pT1N0 stages. Results and limitations Data were collected on 935 patients who met inclusion criteria. GC was used in the majority of the patients ( n = 602; 64.4%), followed by MVAC ( n = 183; 19.6%) and other regimens ( n = 144; 15.4%). The rates of pT0N0 and ≤pT1N0 pathologic response were 22.7% and 40.8%, respectively. The rate of pT0N0 disease for patients receiving GC was 23.9%, compared with 24.5% for MVAC ( p = 0.2). There was no difference between MVAC and GC in pT0N0 on multivariable analysis (odds ratio: 0.89 95% confidence interval, 0.61–1.34; p = 0.6). Conclusions Response rates to NAC were lower than those reported in prospective randomized trials, and we did not discern a difference between MVAC and GC. Without any evidence from randomized prospective trials, the best NAC regimen for invasive BCa remains to be determined. Patient summary There was no apparent difference in the response rates to the two most common presurgical chemotherapy regimens for patients with bladder cancer.
This paper proposes a novel solid-state transformer (SST) having a low-frequency medium-voltage AC (LF-MVAC) port distinctively, which can be as the key equipment for smart distribution networks ...based on LF-MVAC interconnection. The proposed SST has four ports of power-frequency medium-voltage AC (MVAC), LF-MVAC, low-voltage DC (LVDC), and lowvoltage AC (LVAC). In addition to the two-level low-voltage DC/AC converter, the proposed SST is mainly composed of an isolated modular multilevel matrix converter (I-M3C), which can achieve single-stage three-port power conversion. First, the topology of the I-M3C is introduced. Then, a simple modulation scheme is provided to achieve single-stage three-port power conversion, and the operating principles of the I-M3C are given in detail. Additionally, a control strategy based on dual-dq coordinate system is designed, which can achieve stable operation without the complex multi-stage coordinated control and voltagebalancing control strategies. Finally, the effectiveness of the proposed control strategy is verified through a 10-kV/2-MW full power simulation platform, and a 100-V/1-kW scaled-down experimental prototype is built to further demonstrate the correctness of the proposed I-M3C.
Consensus guidelines recommend gemcitabine and cisplatin (GC) or dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (ddMVAC) as equally preferable neoadjuvant chemotherapy before ...cystectomy for muscle-invasive bladder cancer. This study sought to compare the ability of GC and ddMVAC to achieve pathologic response; and to evaluate the benefit of switching regimens after 1 or 2 cycles of the other.
Patients aged ≥ 18 with muscle-invasive bladder cancer (≥ cT2) and who had received either GC or ddMVAC as neoadjuvant chemotherapy followed by cystectomy were retrospectively evaluated using the electronic medical record. Patients who received 1 or 2 cycles of one regimen followed by several cycles of the other regimen before cystectomy were classified as switch therapy patients. This study assessed the rates of pathologic complete response (pCR) and any degree of downstaging.
Among 109 patients who received GC or ddMVAC, 7 (21%) of 33 ddMVAC patients demonstrated pCR, and 19 (25%) of 76 GC patients demonstrated pCR (odds ratio, 1.24; 95% confidence interval, 0.46-3.31; P = .67). Downstaging rates were 39% for ddMVAC and 50% for GC (P = .31). Thirty-three of 36 patients aged ≥ 70 years received GC (P < .001). Four of 7 patients treated with switch therapy showed downstaging, and 2 of 7 experienced pCR.
There was no difference in pCR rates between GC and ddMVAC, and patients were most often able to receive 3 or 4 cycles of treatment. Switch therapy may be of benefit in patients whose disease has a poor initial response.
Consensus guidelines recommend gemcitabine and cisplatin (GC) or dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (ddMVAC) as equally preferable neoadjuvant chemotherapy before cystectomy for muscle-invasive bladder cancer. We retrospectively evaluated 109 patients who received GC or ddMVAC, or GC and ddMVAC (switch therapy). We did not find a difference in response rates for patients treated with GC or ddMVAC, but 4 of 7 patients treated with GC followed by ddMVAC as switch therapy had downstaged disease, and 2 experienced complete response. These findings support the use of GC or ddMVAC based on patient-specific factors; switch therapy may be an option for patients with poor initial response to a single regimen.
The cascaded dc-dc converter is a popular topology for large-scale medium-voltage photovoltaic (PV) system with the advantages of high voltage conversion ratio, high efficiency, great flexibility, ...and independent control capability. However, the absence of optimal string maximum power point tracking (MPPT) operation under power mismatch is a big issue in common centralized control. Furthermore, the cost and time delay are unacceptable resulting from the distance among PV strings in the large-scale PV station and the cascaded dc-dc converter needs to adopt the distributed control method without real-time communication. To this end, by introducing other necessary constraints including voltage constraints, power constraints, and gain constraints on the basis of the distributed MPPT control strategy, a distributed multimode control scheme is proposed in this article. Each submodule (SM) can be switched flexibly between multiple operation modes to maximize the extracted solar energy. Individual string MPPT and autonomous distribution of output voltage are achieved without communication under the proposed distributed control strategy. In this way, optimal operation range is wider, mode switching is simpler, and applicability and robustness are improved. A downscaled prototype and a 35-kV/6-MW simulation system are constructed to verify the effectiveness of the proposed control strategy.
In this article, a hybrid high voltage gain converter module for medium voltage dc conversion in wind energy systems is proposed. The converter consists of step-up resonant circuit with coupled ...voltage-quadruplers to achieve the step-up voltage conversion function. The coupled voltage-quadrupler modules are connected to the resonant circuit via a 1:1:1 high frequency transformer. As a result, high turns ratio transformers are not required in the proposed design while at the same time, the output voltage of each voltage-quadrupler is well balanced due to the shared coupled-inductor. All the primary side silicon carbide (SiC) MOSFETs and secondary side SiC diodes exhibit zero switching losses. The output voltage of the converter module is controlled with variable frequency control. Simulation results on a 4 MW modular design of SiC-based converter system with 3.3 kV/18 kV, 670 kW per module, and experimental results on a laboratory-scale prototype with per-module rating: 500 V/2.7 kV, 3.7 kW are provided to validate the theoretical analysis and to highlight the merits of the proposed work. Results confirmed that a peak efficiency of close to 99% is achieved in both simulation and experimental works.
Sick building syndrome in air-conditioned museum Ali, Azlan Shah; Chua, Shirley Jin Lin; Umar, Mohd Azlan Bin
Museum management and curatorship (1990),
07/2023, Letnik:
ahead-of-print, Številka:
ahead-of-print
Journal Article
Recenzirano
Exposure to indoor contaminants in air-conditioned buildings can cause serious health effects to their occupants. The failure to control indoor air contaminants is one of the factors that contribute ...to poor indoor air quality (IAQ) and is a major contributor to sick building syndrome (SBS) symptoms. This study aims to investigate the relationship between the maintenance of mechanical ventilation and air conditioning (MVAC) that is installed in museums towards IAQ and SBS. Data were collected through site visits and observations with a combination of field measurements and a questionnaire survey. The field measurements results show that several locations in the museums were in a state of heat discomfort. The recorded measurement of air velocity was very low and the average level of HCHO concentrations are above the permissible level. The correlation test between the satisfaction level of MVAC maintenance on IAQ and SBS also shows significant relationships, indicating that MVAC maintenance in the museum affects the comfort and health of the occupants.
Purpose
Neoadjuvant chemotherapy in muscle-invasive bladder cancer (MIBC) patients has proven beneficial in overall survival. However, the optimal regimen is still a matter of debate.
Materials and ...methods
In this retrospective analysis, we evaluate the results obtained in 42 patients treated in our center with 4 cycles of neoadjuvant dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (dd-MVAC) followed by radical cystectomy from August 2015 to October 2020. All patients had cT2 or higher non-metastatic MIBC. Clinical and pathological outcomes are reported.
Results
Of the 42 patients, 90.5% were men (
n
= 38) and the mean age was 65 years. All of them had ECOG 0–1 at diagnosis and most tumors had an initial clinical stage T2N0 (76%). Thirty-six patients (85.7%) completed 4 cycles of neoadjuvant treatment, and 21.4% required a dose reduction. The most frequent adverse event (AE) was grade 1–2 asthenia (81%), while neutropenia was the most frequent grade 3 or higher AE (38%). Complete pathological response (ypT0, ypN0) was achieved in 50% of patients (
n
= 21), and down-staging was observed in 57.1% (
n
= 24). Only one patient presented radiological progressive disease during neoadjuvant treatment (2.4%), and after a mean follow-up time of 31.5 months, 33.3% of patients experienced disease recurrence.
Conclusions
Neoadjuvant chemotherapy with 4 cycles of dd-MVAC is an effective regimen with high rates of pathological complete responses and down-staging along with an acceptable toxicity profile. DD-MVAC should be considered as an alternative to cisplatin and gemcitabine in patients with good clinical performance status.
Medium-voltage (MV) cascaded H-bridge converter (MV-CHBC) provides a transformerless connection to MV distribution system applications such as grid-connected battery energy storage systems (G-BESSs). ...An MV-CHBC consists of multiple series-connected submodules (SMs) forming a wye-connected three-phase topology. The blocking voltage of the utilized power semiconductor modules impacts many converter parameters such as the number of required SMs. Thus, a stepwise design methodology is proposed to select the most suitable high-voltage (HV) module for voltages ranging from 4.16 to 35 kV. Considering that the converter current is constant and independent of the regarded voltage level, 4.16-/2.5-, 13.8-/ 8.5-, 25-/15-, and 35-kV/21-MVA MV-CHBC systems are designed considering HV silicon (Si) IGBT and silicon carbide (SiC) MOSFET power modules rated 1.7 kV up to 10 kV. These designs are evaluated per criteria such as power losses, power density, system complexity, and number of parallel-connected modules. A multiattribute decision-making (MADM) technique is applied to evaluate these designs to select the optimal one according to weights for each criterion. For the 4.16-kV/ 2.5-MVA MV-CHBC system, the 3.3-kV SiC MOSFET-based design is the most suitable one. The 6.5-kV SiC MOSFET-based designs are the optimal ones for the 13.8-/8.5- and 25-kV/15-MVA MV-CHBC systems. For the 35-kV/21-MVA MV-CHBC system, 3.3- and 6.5-kV SiC MOSFET-based designs are the most suitable ones. Experimental results of a 3.3-kV SiC MOSFET-based SM are demonstrated to validate the proposed methodology and MV-CHBC simulations under piecewise linear electrical circuit simulation software (PLECS) environment.
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