def add_kernel_arrays_1D(array_1, array_2):
    """
    Add two 1D kernel arrays of different size.

    The arrays are added with the centers lying upon each other.
    """
    if array_1.size > array_2.size:
        new_array = array_1.copy()
        center = array_1.size // 2
        slice_ = slice(center - array_2.size // 2, center + array_2.size //
            2 + 1)
        new_array[slice_] += array_2
        return new_array
    elif array_2.size > array_1.size:
        new_array = array_2.copy()
        center = array_2.size // 2
        slice_ = slice(center - array_1.size // 2, center + array_1.size //
            2 + 1)
        new_array[slice_] += array_1
        return new_array
    return array_2 + array_1
