The small book Duduan (a term that means "dictatorship" in modern Chinese) was written by the Later Han 後漢 scholar Cai Yong who is very known as politician who tried to save the weak Han emperors to gain back their authority. With his book he defines titles, names and terms of the Han Dynasty court life.

漢天子正號曰皇帝，自稱曰朕，臣民稱之曰陛下．其言曰制詔．史官記事曰上．車馬衣服器械百物曰乘輿．所在曰行在所，所居曰禁中，後曰省中．印岳璽．所至曰幸，所進曰御．其命令：一曰策書，二曰制書，三曰詔書，四曰戒書．
皇帝、皇、王、后、帝，皆君也．上古天子，庖犧氏、神農氏稱皇，堯、舜稱帝，夏、殷、周稱王．秦承周末，為漢驅除，自以德兼三皇，功包五帝，故並以為號．漢高祖受命，功德宜之，因而不改也．
皇帝，至尊之稱．皇者，煌也，盛德煌煌，無所不照．帝者，諦也，能
行天道，事天審諦，故稱皇帝．
The correct title of the Son of Heaven, since the Han Dynasty, is August Emperor (huangdi), he calls himself "we" (zhen), the ministers and the people call him "Below the Steps" (Your Majesty; bixia). His statements are called institutions (zhi) and proclamations (zhao). The historiographers call him "His Highness" (shang). His carts, horses, clothing and the many objects he uses, are called (abbreviated) "Imperial Chariots". The location he stays, is called "His Presence" (xingzaisuo), his living quarters are called "The Forbidden" (jinzhong), the backrooms are called "His Quarters" (shengzhong). The imperial seals are called xi. The location he goes to is called "The Delighted", and where he enters, is called "The Imperial" (yu). His orders are: First, expository writings; second, institutional writings; third, proclamation writings; and fourth, disciplinary writings.
August Emperor, the August, Prince (King), Empress, and Emperor, are all titles of rulers. The oldest Sons of Heaven, Baoxi (Fuxi 伏犧), and the Holy Peasant Shennong, were called the Augusts (huang); Yao and Shun were called emperors (di); the rulers of Xia, Yin (Shang), and Zhou were called kings. At the end of the Zhou Dynasty, Qin inherited the rulership, but it was vanquished by Han. A ruler who is able to unify the virtue of the Three Augusts (Fuxi, Shennong, the Yellow Emperor 黃帝) and to embrace the merits of the Five Emperors (Shaohao 少昊, Zhuanxu 顓頊, Diku 帝嚳, Yao, Shun), can combine these two titles to the expression August Emperor. When Han Gaozu obtained the Heavenly Mandate, his virtue was just completing this objection, and therefore, he did not alter the title (invented by the First Emperor of Qin). [...]
August Emperor is the highest title of honor. "August" (huang) means "brilliant" (huang), the ruler is bright and brilliant with overflowing virtue that reaches every point on earth. Emperor (di) means "truly attentive" (di) in observing the Heavenly Way and obediently serving Heaven. This is why the ruler is called August Emperor (huangdi).
《易》曰：「帝出于震．」震者，木也．言宓（＝庖）犧氏始以木德王天下也．木生火，故宓（＝庖）犧氏沒，神農氏以火德繼之．火生土，故神農沒，黃帝以土德繼之．土生金，故黃帝沒，少昊以金德繼之．．．金生水，故殷湯氏以水德繼之．水生木，故周武以木德繼之．木生火，故高祖以火德繼之．
[...] The Book of Changes says, "The Emperor comes out the Thunder". Thunder is the element wood. That means that Mixi (Fuxi) started to reign under the motto of the virtue of Wood. Wood changes to the element fire, and this is why Shennong continued the reign of Fuxi under the motto of the virtue of Fire. Fire changes to Earth, and this is why the Yellow Emperor continued the reign of Shennong under the motto of the virtue of Earth. Earth changes to Metal, and this is why Shaohao continued the reign of the Yellow Emperor under the motto of the virtue of Metal [... The cycle continues with Zhuanxu (Water), Diku (Wood), Yao (Fire), Shun (Earth), Yu the Great 大禹 (Xia Dynasty; Metal)...] Metal changes to Water, and this is why Tang the Yin (Shang) Dynasty continued the reign of the Xia Dynasty under the motto of the virtue of Water. Water changes to Wood, and this is why King Wu of the Zhou Dynasty continued the Shang Dynasty under the motto of the virtue of Wood. Wood changes to Fire, and this is why Emperor Han Gaozu continues the Zhou Dynasty (Qin is left out) under the motto of the virtue of Fire [...]
帝嫡妃曰皇后，帝母曰皇太后，帝祖母曰太皇太后，其眾號皆如帝之稱．秦漢以來，少帝即位，后代而攝政，稱皇太后詔，不言制．漢興，惠帝崩，少帝弘立，太后攝政．．．后攝政，則后臨前殿朝群臣：后東面，少帝西面，群臣奏事上書，皆為兩通，一詣太后，一詣少帝．
The wife of the Emperor is called Empress (huanghou), his mother is called Empress Widow (huang taihou), his grand mother is called Great Empress Widow (taihuang taihou), and the titles and names of these are all the same like for the emperor. Since the Qin and Han Dynasties, it is custom that the Empress Widow replaces a minor emperor and takes over the politics for him. But the documents she releases are called proclamations, not institutions. At the begin of Han, after Emperor Huidi died, the boy Hong became emperor, and Empress Widow (Lü) took over the regency for him [...] If an empress widow takes over regency, she openly faces the ministers in the audience hall, she faces to the east, while the minor emperor faces to the west. The ministers and officials presenting their memorials, prepare two copies, one is presented to the empress widow, and one to the minor emperor.
漢制，皇子封為王者，其實古諸侯也．周末諸侯或稱王，而漢天子自以皇帝為稱，故以王加之，總名諸侯．王子弟封為侯者，謂之諸侯．群臣異姓有功封者，謂之徹侯，後避武帝諱改曰通侯．
[...] To the governmental institutions of the Han Dynasty belongs the enfeoffment of imperial princes to kings, what is in fact nothing else than the old vassal system. In the last centuries of Zhou Dynasty, the vassals (dukes, marquis) started to call themselves king; and because the Son of Heaven of Han Dynasty is called emperor, the dignity of king was added as a collective designation for vassals. The sons of imperial princes are enfeoffed as marquis. These people the imperial line are called zhuhou marquis, while meritorious ministers and officials are enfeoffed as chehou marquis, a title that was later changed to tonghou marquis because Che was the surname of Emperor Wudi.
帝謚：違拂不成曰隱．．．愛民好與曰惠，聖善同文曰宣，聲問宣遠曰昭，克定禍亂曰武，．．．經偉（＝緯）大地曰文．．．
The posthumous titles of the emperors are:
Disobedient rulers not fulfilling their task are called Yin, "The Retiring".[...]
Sociable rulers loving their people are called Hui, "The Benevolent".
Holy and wise rulers with civil relations are called Xuan, "The Propagator".
A ruler whose voice is strong and far-reaching is called Zhao, "The Prominent".
Rulers able to settle upraisings and quarrels, are called Wu, "The Martial".[...]
Skilled rulers able to span their virtuous net over the whole world, are called Wen, "The Cultured". [...]