def bubbles_from_fixed_threshold(data, threshold=0, upper_lim=True):
	"""
	@ Giri at al. (2018a)

	It is a method to identify regions of interest in noisy images.
	The method uses a fixed threshold.

	Parameters
	----------
	data      : ndarray
		The brightness temperature or ionization fraction cube.
	threshold : float
		The fixed threshold value (Default: 0). 
	upper_lim : bool
		This decides which mode in the PDF is to be identified.
		'True' identifies ionized regions in brightness temperature, while
		'False' identifies in the xfrac data (Default: True).

	Returns
	-------
	Binary cube where pixels identified as region of interest are the True.
	"""
	if upper_lim: return (data<=threshold)
	else: return  (data>=threshold)