As for the liquid water content distributions, the liquid saturations in gas diffusion layers are shown in Fig. 6. For both case1 and case 2, the liquid water appears in the vapor saturation areas which locate between the mid area and cathode outlet area. For both cases, the cathode side exhibits apparent higher liquid water content than anode side does. Moreover, the liquid water accumulates in the porous media under the ribs rather than the gas channels, due to the elimination effects of liquid water in gas channels by convective flows. The maximum value of liquid saturation locates at the edge areas of cathode flow field without coverage by the wavy air channels where the oxygen supply is hindered by both blockage of liquid water in porous media and farther distance for gas permeation. The liquid water content of case 2 shows slightly higher than that of case 1, which is a result of tradeoff between operating temperature and pressure. Increasing temperature alleviates the condensation of water vapor, while the increased back pressure lowers volumetric gas flow rate and enhances liquid water accumulation inside the porous media.

时间: 2023-02-19 09:14:49 浏览: 108
就液水含量分布而言,气体扩散层中的液体饱和度如图6所示。对于case1和case2,液体水出现在蒸汽饱和区,位于中间区域和阴极出口区之间。对于这两种情况,阴极侧表现出明显比阳极侧高的液体水含量。此外,由于液体水在气体通道中被对流流动排除,液体水会积聚在空气通道下的多孔介质中而不是气体通道中。液体饱和度的最大值位于阴极流场的边缘区域,这些区域没有被波浪状的空气通道覆盖,在这里氧气供应受到液体水在多孔介质中的阻塞以及气体渗透的较远距离的双重影响。case2的液体水含量略高于case1,这是操作温度和压力之间的折衷结果。温度的升高减轻了水蒸气的凝结,而增加的背压降低了体积气体流量,增强了多孔介质中的液体水积聚。
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用中文翻译:The detailed temperature distributions under 1 A/cm2 for case 1 are shown in Fig. 11 as an example for analysis. In Fig. 11 (a), the inversely phased wavy flow channels for H2 and air are overlapped in the xz plane indicated with flow directions of each reactants’ channels. The rib areas for anode and cathode sides are also wavy shaped and intercrossed in the front view of xz plane. As a result, there are four kinds of zones in the MEA area when overlapping the anode and cathode flow fields: anode channel / cathode channel (AnC/CaC), anode channel / cathode rib (AnC/CaR), anode rib / cathode channel (AnR/CaC) and anode rib / cathode rib (AnR/CaR). For example, the red dashed line areas in Fig. 11 (a) indicates the AnR/CaR areas where the ribs of MBPP at both anode and cathode sides contact the MEA directly. Fig. 11 (b) shows the temperature distributions in the mid plane of membrane. The high and low temperature areas both present multiple elliptical island shaped distributions with the temperature range of 344 K–346 K. Besides, the calculated 2D temperature distributions in the mid plane of anode and cathode catalyst layers are similar to those in membrane with slight local temperature deviations.

结果,当重叠的阳极和阴极流场时,MEA区域有四种类型的区域:阳极通道/阴极通道(AnC/CaC),阳极通道/阴极肋(AnC/CaR),阳极肋/阴极通道(AnR/CaC)和阳极肋/阴极肋(AnR/CaR)。图11(b)显示了膜中间面的温度分布。高温和低温区域都呈现多个椭圆形岛状分布,温度范围为344 K-346 K。此外,计算出的阳极和阴极催化剂层中间面的2D温度分布与膜中间面的温度分布类似,但存在轻微的局部温度偏差。

用中文翻译:A coupled three-dimensional model is developed to study the internal parameter distributions of the MBPP fuel cell stack, considering fluid dynamics, electro-chemical reactions, multi-species mass transfer, twophase flow of water and thermal dynamics. The model geometry domains include anode MBPP, anode gas wavy flow field (5 parallel flow channels), anode GDL, anode catalyst layer (CL), membrane, cathode CL, cathode GDL, cathode gas wavy flow field (5 parallel flow channels), cathode MBPP and the two-layered coolant wavy flow fields at anode/cathode sides. According to the stack design, the design parameters of wavy flow fields for anode and cathode sides are the same but the phase deviation between their wave cycles presents 180◦. The two wavy flow fields of coolant, at the respective back sides of the anode and cathode plates, form the intercrossed two-layered coolant flow fields inside the MBPP, due to the phase difference of 180◦ between the wave cycles (Fig. 3). The mismatched flow field patterns between the neighbored fluid flows lead to complicated geometry and mesh building. The presented model geometry is divided into several layers (xz plane) according to the different domain materials so that the thin metallic plate and fluid domains with complicated 3D morphologies could be finely meshed layer by layer. As the real geometry of the experimental stack is too large for calculation, the modeled flow field consists of 5 parallel wavy channels, each of which includes 2 wave periods and corresponding inlet/outlet portions as well. To study the detailed thermal behavior of the presented design, the two-layered coolant fluid flow at the back side of the anode plate is considered and so is for the cathode plate. The counter flow operation is conducted where the air flows at the same direction with coolant but the opposite with hydrogen, shown in Fig. 3 (b).

研究MBPP燃料电池堆内部参数分布的三维耦合模型被建立,考虑流体力学、电化学反应、多物种质量转移、水的两相流动和热力学。模型几何域包括阳极MBPP、阳极气体波浪流场(5个平行流道)、阳极GDL、阳极催化层(CL)、膜、阴极CL、阴极GDL、阴极气体波浪流场(5个平行流道)、阴极MBPP和阳极/阴极两层冷却剂波浪流场。根据堆设计,阳极和阴极侧波浪流场的设计参数相同,但其波浪周期之间的相位偏差为180°。阳极板背面和阴极板背面的两个波浪流场形成交叉的两层冷却剂流场,由于波浪周期之间的相位差为180°(图3)。相邻流体流动之间的不匹配流场模式导致复杂的几何和网格构建。所提出的模型几何体根据不同的域材料分为几层(xz平面),以
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Make sure that we grade your HW based solely on your R code script. If we don’t see the correct results when we run your code, you will get 0 point for those questions. 1. Create a R function to show the central limit theorem. This function should have the following properties: - In the argument of the function, you have an option to consider poisson, exponential, uniform, normal distributions as the population distribution. - Depending on the choice of the population distribution in part (1), the function will receive extra argument(s) for the parameters of the distribution. For example, if a normal distri- bution is chosen, the mean and SD are needed in the function argument. Note that each distribution has a different parameter setting. - If the distribution is not selected from (“Normal”, “Poisson”, “Uniform”, “Exponential”), the function needs to print the following error message: check the distributional setting: consider ("Normal", "Poisson", "Uniform", "Exponential") and stop. - The function should give the summary statistics (minimum, 1st quartile, median, mean, 3rd quartile, maximum) of 1, 000 sample mean values for given n values (n = 10, 50, 100, 500). - The result should have the following statement at the beginning, for example, if a normal distribution with mean 1 and SD 0.5 was chosen: ‘‘For the Normal distribution, the central limit theorem is tested’’ where the term “Normal” is automatically inserted in the statement based on the argument. And the output should have the following form: For the Normal distribution, the central limit theorem is tested When n=10: Min. 1st Qu. Median Mean 3rd Qu. Max. 0.5187 0.8930 1.0016 0.9993 1.1019 1.4532 When n=50: Min. 1st Qu. Median Mean 3rd Qu. Max. 0.7964 0.9508 1.0010 0.9997 1.0493 1.2309 1 When n=100: Min. 1st Qu. Median Mean 3rd Qu. Max. 0.8534 0.9679 0.9972 0.9992 1.0325 1.1711 When n=500: Min. 1st Qu. Median Mean 3rd Qu. Max. 0.9258 0.9836 1.0006 0.9997 1.0154 1.0678 I Using your own function, test the N(−1,0.52) and the Unif(−3,6) case.

用中文总结以下内容: A number of experimental and numerical investigations have been conducted to study the MBPP stack and wavy flow field characteristics with various designs [10,11]. T. Chu et al. conducted the durability test of a 10-kW MBPP fuel cell stack containing 30 cells under dynamic driving cycles and analyzed the performance degradation mechanism [12]. X. Li et al. studied the deformation behavior of the wavy flow channels with thin metallic sheet of 316 stainless steel from both experimental and simulation aspects [13]. J. Owejan et al. designed a PEMFC stack with anode straight flow channels and cathode wavy flow channels and studied the in situ water distributions with neutron radiograph [14]. T. Tsukamoto et al. simulated a full-scale MBPP fuel cell stack of 300 cm2 active area at high current densities and used the 3D model to analyze the in-plane and through-plane parameter distributions [15]. G. Zhang et al. developed a two-fluid 3D model of PEMFC to study the multi-phase and convection effects of wave-like flow channels which are symmetric between anode and cathode sides [16]. S. Saco et al. studied the scaled up PEMFC numerically and compared straight parallel, serpentine zig-zag and straight zig-zag flow channels cell with zig-zag flow field with a transient 3D numerical model to analyze the subfreezing temperature cold start operations [18]. P. Dong et al. introduced discontinuous S-shaped and crescent ribs into flow channels based on the concept of wavy flow field for optimized design and improved energy performance [19]. I. Anyanwu et al. investigated the two-phase flow in sinusoidal channel of different geometric configurations for PEMFC and analyzed the effects of key dimensions on the droplet removal in the flow channel [20]. Y. Peng et al. simulated 5-cell stacks with commercialized flow field designs, including Ballard-like straight flow field, Honda-like wavy flow field and Toyota-like 3D mesh flow field, to investigate their thermal management performance [21]. To note, the terms such as sinusoidal, zig-zag, wave-like and Sshaped flow channels in the aforementioned literatures are similar to the so called wavy flow channels in this paper with identical channel height for the entire flow field. The through-plane constructed wavy flow channels with periodically varied channel heights are beyond the scope of this paper [22,23].

以下是一篇即将投稿Minerals期刊(MDPI出版社)的论文初稿的部分内容,请按照该期刊对论文格式的要求,将以下内容进行压缩凝练(注意:可对内容进行删减,对错误进行修正,对语句顺序进行调整,符合美式英语标准,符合英语母语者语言习惯,句子简明易懂,术语使用准确,保留文章结构、不偏离论文主要内容): Rocks and ore components directly enter the soil and water system sediments through physical weathering and chemical weathering, and the geochemical anomalies originally present in the rocks further spread with the entry into the soil or directly into the water system, forming soil anomalies and water system sediment anoma-lies.Geochemical anomaly detection is essentially the detection of signal anomalies in geochemical data, which refers to finding out the anomalous distribution of chemical elements themselves and the anomalous distribution of multiple elements in combination through feature extraction and analysis processing of geochemical data in the study area, and reflecting the mineral distribution through the distribution of geochemical ele-ments.Through the method of geochemical anomaly finding, the detected anomalies may contain information indicating specific minerals, which facilitates the rapid tracing of prospective areas and favorable areas for mineralization, identifies possible mineralizing elements and distribution characteristics in the work area, provides basic information for the strategic deployment of mineralization search, and provides good indications for later mineralization search.

class PPO(object): def __init__(self): self.sess = tf.Session() self.tfs = tf.placeholder(tf.float32, [None, S_DIM], 'state') # critic with tf.variable_scope('critic'): l1 = tf.layers.dense(self.tfs, 100, tf.nn.relu) self.v = tf.layers.dense(l1, 1) self.tfdc_r = tf.placeholder(tf.float32, [None, 1], 'discounted_r') self.advantage = self.tfdc_r - self.v self.closs = tf.reduce_mean(tf.square(self.advantage)) self.ctrain_op = tf.train.AdamOptimizer(C_LR).minimize(self.closs) # actor pi, pi_params = self._build_anet('pi', trainable=True) oldpi, oldpi_params = self._build_anet('oldpi', trainable=False) with tf.variable_scope('sample_action'): self.sample_op = tf.squeeze(pi.sample(1), axis=0) # choosing action with tf.variable_scope('update_oldpi'): self.update_oldpi_op = [oldp.assign(p) for p, oldp in zip(pi_params, oldpi_params)] self.tfa = tf.placeholder(tf.float32, [None, A_DIM], 'action') self.tfadv = tf.placeholder(tf.float32, [None, 1], 'advantage') with tf.variable_scope('loss'): with tf.variable_scope('surrogate'): # ratio = tf.exp(pi.log_prob(self.tfa) - oldpi.log_prob(self.tfa)) ratio = pi.prob(self.tfa) / (oldpi.prob(self.tfa) + 1e-5) surr = ratio * self.tfadv if METHOD['name'] == 'kl_pen': self.tflam = tf.placeholder(tf.float32, None, 'lambda') kl = tf.distributions.kl_divergence(oldpi, pi) self.kl_mean = tf.reduce_mean(kl) self.aloss = -(tf.reduce_mean(surr - self.tflam * kl)) else: # clipping method, find this is better self.aloss = -tf.reduce_mean(tf.minimum( surr, tf.clip_by_value(ratio, 1.-METHOD['epsilon'], 1.+METHOD['epsilon'])*self.tfadv))

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